Life Histories 

A chapter from the electronic book:  Life Histories of Familiar North American Birds

Pine Siskin
Carduelis pinus  

Contributed by Ralph S. Palmer
[Published in 1968: Smithsonian Institution United States National Museum Bulletin 237 (Part 1): 424-447]

The pine siskin is a social bird the year round. Breeding individuals join in social flocks away from the nesting territory, and they sometimes feed in the tree where the nest is situated. These social groups are small, up to a half dozen birds, not the large flocks commonly seen outside the breeding season. From late summer to late winter the pine siskin associates, roughly in descending order of frequency, with the redpolls, the goldfinches, the two crossbills, the purple finch, the cedar waxwing, and, very occasionally, the juncos. Except for the first two mentioned, the association usually is brief and may break off whenever a mixed flock takes flight. A common situation is to find the few siskins in the flocks of the other species, especially when goldfinches or redpolls are plentiful and the siskins few.

The siskin is a relatively high and swift flier, often crossing from ridge to ridge or peak to peak in direct flight far above the trees in the intervening area. The flocks are compact, and all members execute long undulating sweeps in unison. Usually the birds fly silently, but now and again one or many may utter a sharp lisping call-note that carries well.

The decision to alight seems to come abruptly, and the flock drops down into the trees to rest or feed. It is common for the birds to be more vocal on alighting, and again as they depart. Often when feeding, there are no birds in flight; at other times part of the flock may take wing and pass over those still feeding to other food trees. As the birds thus go "leapfrogging," the entire mass of the flock of busy, lisping birds appears to flow through the forest. Then all of a sudden the lisping ceases and the flock is silent; it takes flight with a very audible whirring of wings and flies rapidly away.

By observing alders in Strawberry Canyon at Berkeley, Calif., in February, T. L. Rodgers (1937) provides a description of siskin habits that applies generally:

It began to appear as if the regular procedure of the birds was to alight in the top of a tree, forage down to the lower limbs, never spreading over an area more than 12 or 15 feet across, and then by means of a circular flight move to the top of another tree and forage down it. Although this was the commonest method, they were also seen to forage in a nearly horizontal line through a group of trees without foraging through any of them completely; they foraged up through a tree, and then moved by a direct route, at times even "flowing" from one tree to the next after the manner of a flock of Bush-tits. The direct flights of the flocks were either to trees far away or to those ten or fifteen feet off. This seems to bear out the idea that "circle flights" are survey flights.

The siskin's gait seems much better adapted to climbing about tree tops than to ground feeding. On the ground it walks with very short steps interspersed with occasional little hops, and its body almost seems to cling to the ground.

Many authors have commented on the siskin's tameness and boldness in its relations with human beings. Brooding females usually can be approached within inches before they leave the nest. Exceptional, however, was the experience of F. H. Allen (1888) at Newton Mass., in late April. He observed two siskins near a heap of hops by the roadside. One flew away on his approach; the other, though able-bodied and in good condition, allowed itself to be approached closely, stroked, and caught in the hand. Allen queried: "Was this bird affected by the hops. . .?" E. R. Davis (1926) reported siskins at Leominster, Mass., to be remarkably tame in late fall. He says:

In a short time the birds came to regard me as their friend, and in the days that followed grew to be exceedingly sociable and to lose every vestige of fear. Whenever I would appear at the window, or step outside the door, down they would come and, settling upon my head, shoulders, and arms, would peer anxiously about for the food that they had learned to know I held concealed from them in a box, dish, or other receptacle. The moment I removed the cover or exposed the food, they would make a dash for it and the usual scrapping program would be on. Nor was it at all necessary for me to go outside the door. . . . In a short time the siskins discovered this opening [in a window pane], and it was only necessary for me to draw the slide when one after another would come right into my kitchen, and soon one or more of them would be perched on my head or shoulder, or hopping around on the desk where I was writing, looking for the handful of seeds that they all knew was forthcoming. . . . Now and then some members of the flock would elect to spend the night in the warm room, sleeping on the clothes-line, stretched across the room a little below the ceiling. On such occasions they seemed to be without fear and totally oblivious to people moving about the room, often within a few inches of them, turning on or snapping off electric lights.

The interested reader may want to read all of the above quoted article by E. R. Davis. He carried out a series of conditioned reflex experiments. Only a paragraph about one of these is quoted here; it concerns a button rigged to release a small batch of seeds when pushed:

For quite a while the thing remained a puzzle to them. Finally, one of them happened to notice that push-button, which was a different colored wood from the rest of the contraption. He sidled up to it, looked it over for a moment, then gave it a "biff." This released the catch on the other side and down at his feet came a little handful of seeds. This frightened him, of course, and he flew away, only to return a minute later, eat the seeds that had fallen down the chute, and then tried the "press the button" arrangement again. It was not long before several of the flock learned the secret, but it was quite a while before they became used to the seeds falling down at their feet, so that they were not afraid, and would proceed to eat them without first flying away a few inches.

A siskin's life is not always easy. During severe weather in March and April, 1939, many siskins died on Mount Desert Island, Maine (R. S. Palmer, 1949). Winter deaths, presumably from eating a poisonous chloride are discussed under food. Various authors have reported destruction of nests, eggs, or young by wind, sleet, and rain. Heavy rains have killed young after they departed from the nest. Several observers, on finding nests empty and sometimes damaged, have suspected predation by the red squirrel and the blue jay. The domestic cat is a known predator. The cowbird, too, is a hazard, since its egg or chick in a siskin nest is detrimental to the siskin's nesting success. Both parent siskins treat the young cowbird as one of their own. At Wenatchee, Wash., R. T. Congdon found a young siskin that had died after a foot became entangled in the nest lining.

E. R. Davis (1926) described siskin actions at the sight of a northern shrike at Leominster, Mass., in winter:

It was wonderful how quickly they would detect one of these birds in the vicinity, or even at a great distance. Instantly, if one of them appeared in the sky or on a distant tree, all activity ceased among the Siskins, and each bird, intently watching the enemy, would literally "freeze" to the spot where he was sitting, hardly moving a feather until the enemy had disappeared. On more than one occasion I have had them "freeze" in my hand, where they had been sitting when the danger threatened.

Aggressiveness is a marked siskin trait at feeding stations. Davis (1926) placed food on a shelf 3 feet square and found that "the bird that first reached the place seemed to consider himself the sole owner of the entire stand, and woe to the individual that dared dispute his claim." When feeding with purple finches the siskins are bold and usually hold their own. Generally they feed together peaceably, but now and again a siskin takes the offensive and darts at a purple finch, scaring it away. Perhaps the siskin's sharp bill gives it authority. In feeding with evening grosbeaks, the siskins keep their distance and show pugnaciousness only among themselves.

Territory.--Siskins go in flocks containing a few to well over a thousand individuals. Flocks of 50 to 200 are common. At the close of the breeding season--usually early summer--the birds generally leave the breeding localities, although the extent and often direction of this movement is unknown. The birds may occur in or pass through the nesting area again in autumn. Large-scale incursions in the postbreeding period have not been noted as frequently as autumn and winter invasions. However, in Alberta beginning in mid-June and lasting into August, 1921, large numbers of siskins moved into the park country of the prairie where no evergreens occur except for small patches along river bottoms. F. L. Farley (1921) reports that at almost any hour of the day one could see large flocks, "whirling here and there" in redpoll fashion. They would feed, then take flight suddenly.

In parts of the siskin's range near and along the Pacific coast, the species occurs in many localities all year, but a goodly share of the population moves altitudinally to the lowlands in autumn and to higher elevations to breed in spring. The highest altitudinal record is for a siskin that Taylor and Shaw (1927) found dead at approximately 11,000 feet on Mount Ranier, Wash.

The siskin's center of abundance is from the Rocky Mountains westward. Part of the population in the interior of the continent shows a more or less northwest-southeast movement in autumn and the reverse in spring. Thus it seems likely that the species may have spread eastward, as the evening grosbeak did at a later period, but before the event could be chronicled. M. H. Swenk (1929) wrote:

Judging from the fact that in various falls that they have occurred in Nebraska the Pine Siskins usually have been seen first in the more westerly and northerly parts of the state, and later in the more southeastern localities, and also from the further fact that they may reach western or central Nebraska commonly in seasons when they are uncommon or absent in extreme southeastern Nebraska, it is probable our Pine Siskin winter visitors are birds that summer in the Black Hills and those parts of the Rocky Mountains at a corresponding latitude, or northward.

The fall and winter wanderings, especially in the East, are so irregular in occurrence and so variable in extent that it is difficult to define the species' usual range as compared to its total range. At any rate there is usually some movement--vertical migration in mountains, horizontal elsewhere, both unpredictable regarding the amount or direction. In some years these movements become southward incursions of vast extent. Dorothy Mierow (1946) summarized as follows:

Some years are marked by exceptional flights of these birds southward. In 1896, enormous flocks were found in Louisiana, South Carolina, Missouri, and Illinois. Again in the year 1907, notable for its cold spring, flocks were observed in Florida, Tennessee, Ohio, Michigan and Missouri. This year they nested in Nebraska. The season of 1922-23 was characterized by an abundant crop of beech nuts and wild fruits, and again the siskins appeared in large numbers in Alabama, Virginia, Ohio, Wisconsin, North Dakota, and Nebraska. They were conspicuous by their absence from Yosemite National Park, California, in the fall of 1923. In 1925, they were seen in Kentucky and Michigan, and they nested in North Dakota and also at Ithaca, New York. There were abundant spruce, fir, and hemlock seeds in the Great Smokies of Tennessee in 1937. Siskins, usually rare in Tennessee, appeared in thousands during November. In other years, too, there were great flights at one place or another, but in these particular years the movement was most marked.

During an incursion into the southeast in winter of 1946-47, R. L. Weaver (1948) saw five birds in Orange Park, Clay County, Fla., probably the southeasternmost record.

The pine siskin is commonly stated to wander continually throughout the nonbreeding season, especially during fall and winter. But when food is plentiful, many observers have noted that siskins will remain in one particular area over a long span of time. At Northampton, Mass., B. M. Shaub (1951a) analyzed his banding data for early 1947 as follows:

An examination of this record will show at once that the birds with which we were working were not, in all probability, wandering winter visitors or transients as they generally have been described. On the other hand they more-or-less settled down in Northampton and vicinity for the winter and spring. . . . [Seven banded individuals] were with us rather regularly over a period of 2 1/2 months, although it is possible that they could have made visits to other localities nearby and as often returned.

Courtship.--The pine siskin probably begins breeding when a year old, but data from banded birds to prove this are scant. Richard Harlow (1951) states that there is abundant evidence that the crossbills and siskin have no definite breeding ranges. He writes: "I do not know of any locality in our northeastern and northern forests where one can say, 'We will find the pine siskin here this year.'"

M. H. Swenk (1929), in his study of this species in Nebraska, correlated breeding records with temperatures of the months of March, April, and May. If the mean temperatures for April were subnormal, the siskins might remain and breed; the same might happen if supernormal April temperatures were followed by subnormal May temperatures. Nebraska is, of course, outside the area where the siskin ordinarily may be expected to breed. Usually the birds are numerous--often abundant--in areas where food is plentiful. The flocks contain both sexes. Scattered flocks tend to join, forming larger ones. By late January of most years, in localities all across the continent, the thin lispy calls of the siskin are augmented by a warbled song. At this time the flocks break up into smaller ones, then into groups of three to five birds, then into pairs.

There is considerable fighting and chasing when the flocks start to disintegrate. At Rutherglen, Ontario, Mrs. Lawrence notes: "In the midst of all this sweet singing, two birds swing into the air in an extensive 'cloud chase,' their movements tightly synchronized as they alternate in the roles of pursuer and pursued."

Perhaps anticipatory to courtship- and nest-feeding is a performance observed in late April in Everett, Wash., by M. R. Thayer (1911): "Our attention was called to three birds on a [trellis] cross-bar about seven feet from where we stood. Two were close together and the third a little apart, and all three were opening and closing their bills, stretching them wide as if yawning and closing them with a snap. Before we had time to consider what it might mean, the two turned toward each other and touched their bills in a most lover-like manner. They were quiet a moment, then one opened his bill wide again and they both flew away followed by the third. . . ."

Courtship feeding begins while the birds are still in flocks or small groups. On Feb. 5, 1948, at Rutherglen, Ontario, Mrs. Lawrence noted: "The female sat on a twig. Presently the male alighted on the same twig, hopped up to her and offered her a small particle, of what I could not see. She crouched and, with trembling wings, accepted the offering."

The birds are still in flocks or groups when courtship flight with song reaches its fullest development. Two paragraphs from Mrs. Lawrence's notes describe it well: "With a beam of sunshine illuminating his golden flashes, the male rose into the air with tail spread wide and wings in a blur of rapid motion. To the accompaniment of a flight song which seemed to express far more musical adoration than could be contained in so small a body, he described circle after circle around his chosen mate. That the female reflected none of her partner's emotion in no way seemed to dampen his ardor and, after he dropped on to a twig from pure exhaustion to catch his breath, a few moments later he rose again in a repeat performance no less ecstatic than the first.

"None of the flight song performances I saw ended in copulation. When that took place in my presence, it was an anticlimax to what I had previously seen. Two birds came to the salt lick and one of them perched in a bush. That very instant the male alighted directly upon the first bird by the pouncing technique without any sort of preliminaries. Copulation took place with both birds trembling violently. When it was over, the female begged and the male, with nothing in the bill, performed a token feeding. The female shook herself and both birds hopped down on the ground where the male strutted a little with raised head feathers."

Formation of the pair bond involves symbolic feeding, sexual flight, and song, and it occurs while the birds are in social groups. Single brood monogamy is certain, but how much longer the pair bond lasts is not known.

Nesting.--At times Siskins nest as isolated pairs. More usually, nesting is somewhat a colonial affair, with the nests rods apart. Adults join in social flocks away from the nests.

Typically, the nest is at middle height in a conifer, well out, and concealed on a densely foliaged horizontal limb. The most frequent departure from this pattern is for the nest to be located lower down, but when this happens it is still usually above 8 feet from the ground. Commonest choices for nesting are hemlock, pines, spruces, firs, cedars, redwood, cypress, and wild lilac. Introduced conifers, also transplantings of native trees, are occupied in addition to natural stands. Deciduous trees are used for nesting occasionally. For example, the siskin has nested in box elder in New Mexico (F. M. Bailey, 1928) and North Dakota (R. Reid, 1929), in maples and oaks in Oregon (C. Keller, 1891), in maple in Washington (R. T. Congdon), in the very top of a 50-foot eucalyptus in California (Carriger and Pemberton, 1907), among cottonwoods in Montana (A. A. Saunders, 1912, 1921), and two nests in lilacs in Colorado (F. M. Dille, 1900). The highest nests are at about 45 to 50 feet. In manuscript notes, S. F. Rathbun recorded a nest in Washington only 4 1/2 feet above ground in a stunted cedar. The lowest record at hand is of a nest in Iowa, recorded by Dales and Bennett (1929) as only 3 feet up in a 4 1/2-foot cedar on a lawn. During resting periods the birds go to tree tops.

The female chooses the nest site and is accompanied by the male as she brings nesting material. At times the birds return to social life in flocks; also, other siskins occasionally accompany the nesters on flights to the nest tree. As C. W. Bowles (1903) puts it, several paris may be "superintending" when one is building. The small nesting territory is used for copulation--although this occurs elsewhere, too--and nesting; in addition, the male feeds his mate there during incubation and the period until the young attain flight. The defense of territory is developed slowly, being weak until after the nest is built. Weaver and West (1943) write:

During nest building the male had been quite attentive to the female and never left the nesting area for very long periods, and he did not seem to be very closely associated with any of the other siskins or flocks which fed near the nest tree. After the eggs were laid, he would leave the area for short periods, which became longer as incubation progressed. He frequently returned in company with one of several other siskins. The female would chase these birds, as would the male, if they came too close to the nest. On several occasions, he flew off with these birds after feeding her on the nest. Other birds would enter the general nesting area and feed with one or both of the mated birds, unmolested.

As is common with a number of early nesters, the structure that the siskin builds is rather large in proportion to the size of the builder and usually well concealed in foliage. It is fairly well put together, generally somewhat flat, and often not very securely fastened to the branch. The foundation and sides consist of such materials as twigs, rootlets, and grass; the lining consists of fine rootlets, hair, fur, feathers, and other fine-textured material. The finer material, at least, is often gathered on the ground. Dales and Bennett (1929) saw a siskin dismantling an old goldfinch nest and using the materials in new construction.

Numerous photographs and descriptions of nests have been published. A good example of the latter is C. H. Morrell's (1899) of one found in March in Nova Scotia:

It was saddled on the limb and radiating twigs but not attached to them. Considering the size of the bird, it is quite large, rather flat, and bears no resemblance to. . . [Goldfinch nests], measuring as follows: height, 1.63 inches; depth, .75; outside top diameter, 4 inches; inside top diameter, 2 inches. It is constructed mainly of dark pendulous tree-moss, with some fulvous bark from weed-stalks, plant-down, usnea, and other mosses. About the bottom of the nest is [sic] woven a few spruce twigs. The lining is entirely the pendulous moss.

From Eureka, Calif., R. R. Talmadge writes of two nests that he considered distinct from all others he had found. The first was composed of fine grayish rootlets with a minimum of plant fiber and lined with black horsehair. The other was similar, but was lined with red hair from cattle that were in the immediate area. Most of the nests discovered were similar in composition, but the lining was mixed, not distinct as in these two.

According to Weaver and West (1943), at Hanover, N.H.:

Three days were required to complete the outer layers and bottom of the nest. On the fourth day, lining materials were added. Several attempts to break off small twigs from the nest branch were observed. After the fifth day, materials were added to the nest sporadically until the eggs were laid. On the seventh day the female began making trips to the nest without materials and sitting on it for short periods. This procedure continued with the trips to the nest becoming more frequent and the time spent on the nest increasing to as much as fifty minutes before the tenth day, April 18, when the first of the two eggs was laid. The second egg was laid on the following day.

Eggs.--The data summarized from Mierow (1946) plus other available published and unpublished information through 1954, indicate that three-egg clutches predominate, about two-thirds as many have four eggs, a third as many have two, that clutches of five are rare but occur more often than those presumed complete with a single egg. C. W. Bowles (1903), for example, mentions sets of one (complete?), three, and four in Washington, and stated that three seemed most common. Carriger and Pemberton (1907), writing of San Mateo and San Francisco Counties, Calif., states that the "average set seems to be three eggs, but four is also a common number. Several sets of two eggs were taken in advanced states of incubation, and also two sets of five, but these are rare." There seems to be no geographic variation in clutch size, but it is difficult to assess the data since most sets observed were from Pacific coastal states.

Carriger and Pemberton (1907) write: "The eggs are a pale greenish blue several shades lighter than the eggs of Astragalinus [goldfinches], and are marked with chocolate spots and irregular blotches, with a number of pale lavender blotches which appear to be beneath the surface of the shell. Eggs vary from very nearly unmarked, to well marked about the larger end and sparingly over the whole surface. The average size of all eggs at hand is .63 X .48 inches."

In a manuscript note, Robert R. Talmadge of Eureka, Calif., states: "Several sets which I have found had one or two unmarked eggs. The markings vary from small blackish spots to semi-elaborate scrolling of dark sepia and lavender."

All egg data at hand indicate that complete sets of fresh eggs usually are to be found in the United States and Canada from early April to early May. Eggs in March, or indications of their probable  occurrence then, are as follows: young nearly ready to leave the nest March 19 at Woodstock, Vt. (E. H. Forbush, 1929); nest nearly completed March 15 (had three eggs on the 31st) and another started March 18, at Lincoln, Nebr. (M. H. Swenk, 1929); siskin gathering nesting material March 16 in San Francisco County, Calif. (M. S. Ray, 1916); nest completed March 11 had three eggs on March 18, also nest with two nearly fledged young on April 13, in Lewis County, N.Y. (C. H. Merriam, 1878); nest with two eggs and two newly hatched young March 28 or 29, at Tacoma, Wash. (J. H. Bowles, 1924); clutch of four on March 29 in Nova Scotia (C. H. Morrell, 1899); nest with two eggs taken on unstated March day in Ontario (Baillie and Harrington, 1937); and unstated number of eggs the last of the month in Vermont (Tracy in Mierow, 1946). Fresh eggs in May and early June are common but why many fresh clutches have been found in California in early June is a matter for speculation.

The set of eggs of the pine siskin varies from three to six; sets of four and five are most frequent. They are ovate with some tendency toward short-ovate and have very little lustre. The ground color is greenish-white or bluish-white, delicately speckled and spotted with "light cinnamon drab," "cinnamon drab," "warm sepia," or "Verona brown," with a few thin scrawls of black. In general, the markings are concentrated somewhat toward the large end where they often form a loose wreath; rarely an egg is found that is almost immaculate.

The measurements of 50 eggs average 16.6 by 12.4 millimeters; the eggs showing the four extremes measure 18.08 by 13.1, and 14.3 by 11.3 millimeters.

Eggs are laid on successive days. Weaver and West (1943) say that at Hanover, N.H., both eggs of a two-egg clutch "were laid before nine o'clock in the morning. Incubation began upon the laying of the first egg and the young hatched thirteen days later, one day apart. . . . The danger from freezing of the eggs would appear to be lessened with incubation beginning upon the laying of the eggs."

Only the female has an incubation patch and she alone incubates. Weaver and West (1943) write: "During incubation, the female stayed very close to the nest. The longest observed period that the female was off the nest for the entire period of incubation was eight minutes. She was fed by the male during incubation, and this permitted long uninterrupted periods on the nest; in fact, he began feeding her on the nest the day before the first egg was laid and in one instance was observed to feed her while she was off the nest before the eggs were laid."

Hatching is described by the same authors (1943) as follows: "Just prior to hatching, the female stood up on the edge of the nest and looked at the eggs a great many times. Hatching occurred early in the morning, before 7:30 a.m., or possibly during the night. There was no sign of the egg shell in the nest, but later a small piece was found under the tree.

Young.--In the above-mentioned nest, "feeding of the young began very soon after hatching, possibly within the hour." Weaver and West reported that, during the first few days after hatching, the female fed the young about every 10 to 15 minutes, but near the end of the nesting period feedings were about an hour apart. For the first 7 or 8 days the male fed the female on the nest and she fed the young; he increased his trips with food to twice an hour, and made even three or four trips per hour toward evening.On the 7th or 8th day he began to feed the young directly. After the 10th day, the male was not seen to feed the female and she began to forage for herself and the young.

The usual method of male feeding female when the young are small has been reported from Berkeley, Calif., by T. L. Rodgers. The bird on the nest hears ti-er, ti-er from the mate in another tree, and replies ti-er. They call back and forth three or four to a dozen times, and the food bearer flies to a position a few feet from the nest and utters one or more plaintive pseee notes. Then, while both are silent, it hops quietly toward the brooding bird. She flutters her wings and begs and the feeder regurgitates. Rodgers (1937) states: "The feeding process continued by the clasping of the bills of the two birds, the upper and lower mandibles of one just closing the complete gape of the other. Three or four such contacts were made, and, between each, the bird doing the feeding gulped as if bringing more food into its mouth. The bird then flew away, and the brooding bird sat quietly for eight or ten seconds before proceeding to feed the young."

This regurgitative feeding of the brooding female by the male was observed at close range at Sioux City, Iowa, by Dales and Bennett (1929), who pointed out that the process is a comparatively long one. Their description of a feeding ends thus: "Toward the end of the feeding as the male withdrew his beak from the female's mouth a string of saliva-like substance stretched between the two bills; this was immediately sucked in by the female. There must have been considerable of it, for there seemed to be a flow of it for nearly fifteen seconds. Then the male flew away."

The food-bearing male sometimes is accompanied by other siskins who do not trespass in the small defended area around the nest. They perch in the nest tree, or in nearby trees; they also accompany the male when he departs, as several observers have noted. The female also joins social groups.

Weaver and West state that the young never were left unprotected more than 11 minutes, that during the first week the female's usual duration of absence was 3 minutes. She kept the nest clean by eating all excreta for the first 7 or 8 days; later it became fouled because neither parent removed the droppings. T. L. Rodgers (1937) observed the eating of the droppings. He states that the nest was kept clean during the first 8 days and, from the 9th day on, no droppings were taken from the nest and they accumulated there.

Data on the growth and development of young siskins have not been published in detail. In New Hampshire, Weaver and West (1943) report that the brood of two young they studied showed their first fear reactions about in their 6th day. The young became very active during the last 4 days of nest life and the female then spent little time brooding them. They took turns exercising and stretching their wings, also walking on the nest rim. In their haste to be fed, they sometimes fell over the side and grasped the outer structure and pulled themselves back again. They say that "The adults seemed to approach the nest rather deliberately during the last 2 days, seemingly coaxing the young to such daring feats."

Both young left the nest 15 days after the first hatched; thus one was a nestling 14 days (it probably departed prematurely) and the other 15, which may be the usual initial flight age. One young was seen being fed in the nest tree an hour or so after both had left the nest. Other observers have indicated that the young are with the parents and fed several days, or longer, but the span of time from nest-leaving to independence remains unknown.

Whether our bird, like the Old World siskin, Spinus spinus, is double-brooded is still a moot point. There is a strong probability that it is--at least in some years--and that the birds may change localities between nestings. E. H. Forbush (1929), without direct support, says: "One brood yearly, probably two in many cases." Suggestive is a single sentence by William Brewster (1938) relative to the siskin on Aug. 9, 1873, at Lake Umbagog on the Maine-New Hampshire boundary: "A male shot this morning was unmistakably breeding and yet full-grown young are about in considerable numbers." As already shown, the siskin is an early nester; also, fresh eggs are fairly common as late as early June in some localities and seasons, especially Pacific coastal states, and eggs or nestlings in July have been recorded for a number of localities widely spaced geographically. Here are some late breeding records: set of five eggs July 22 in Ontario (Baillie and Harrington, 1937); pair of siskins seen copulating July 30 on Forrester Island, Alaska (Willett, in Mierow, 1946); nest with young August 4 in Faith Valley, Calif. (Bassett, in Mierow, 1946); birds in breeding condition carrying nesting material, July 15 - August 14, in the Porcupine Mountains, Mich. (W. B. Barrows, 1912); four young left the nest August 19 at Bozeman, Mont. (A. A. Saunders, 1921); clutch of three fresh eggs August 14 at Tacoma, Wash. (C. W. Bowles, 1903); and nests "containing young in early September," also at Tacoma (J. H. Bowles, 1924). Omitted are various late dates for adults reported as seen "feeding young"; it is assumed they are for young that have been flying, and for an unknown length of time.

It seems that the very long span of breeding dates can hardly be explained in terms of replacement layings after a loss of an earlier clutch or brood. More likely, either some birds breed twice in some years or different parts of the population breed at different times.

Plumages.--There is little sexual dimorphism although, after the juvenal stage, and presumably among birds of equal age and state of plumage wear, males are usually more brilliantly colored. This applies especially to the yellow portions of the wing and tail.

Breeding adults are grayish brown above, heavily streaked with dusky; the paler rump is often tinged with yellow. Wings and tail are mainly dusky. The basal portions of the flight feathers are yellow, and are conspicuous in flight but almost entirely concealed when the birds are at rest. There are two narrow whitish wing bars. Underparts are whitish, heavily streaked with dusky except from the abdomen posteriorly when it is often plain. The bill is brownish or dusky at the tip, becoming paler (flesh colored or bluish) toward the base, especially the lower mandible. The iris is brown. Legs and feet vary greatly in color, but usually are medium light to a darker shade of brown. This breeding condition is a result of wear and fading of the plumage acquired months beforehand by a partial post-juvenal molt in the case of young birds and a complete post-nuptial molt in the case of adults.

At Rutherglen, Ontario, 1948, siskins were plentiful and nested. Mrs. Louise de Kiriline Lawrence saw the first flying young on May 10. On May 22 females with incubation patches were noted going into molt and, in general, acquiring fat--first on the abdomen, then on the axilla, and last on the fulcrum. The birds then left the area, the last seen on June 3.

After the postnuptial molt--details of it have been described by T. and E. McCabe (1928)--the new fresh plumage has these characteristics: orange-buff wing bars; strong dusky markings and yellowish edges on back feathers; buffy or yellowish tint on abdomen (which may be either heavily or lightly streaked or plain); and buffy chest and flanks.

Although the natal down has been observed quite often, apparently no description of it has been published. The photographs in the article by T. L. Rodgers (1937) indicate a well developed nestling down exists.

The development of the juvenal plumage has not been described; it is developed to the point that initial flight occurs at 15 days of age. This plumage is more buffy and warmer in general tone than the worn breeding plumage of the adults it associates with, so the two age groups then can be distinguished afield. After wear and fading, it is very similar in general aspect to that of worn adult plumage.

The juvenal plumage is worn a long time, probably two months according to Dwight (1900), but the exact time is hard to determine because of the irregular breeding season. Rockwell and Wetmore (1914) state that immature birds were still in molt in Colorado the first week in October. They mention young out of the nest July 18, but since the duration of molt is not known, one cannot estimate the time lapse before it began. Winter flocks of incursion visitants usually are preponderantly birds of the year, but this is hardly a clue in interpreting A. T. Wayne's (1906) comment for the period Dec. 12, 1896, to the following mid-March in South Carolina: "Between these dates many of the birds taken seemed to be in a state of perpetual molt."

According to Dwight (1900), there is a partial post-juvenal molt in August in eastern Canada involving body plumage but not wings and tail. The first nuptial stage, therefore, is this combination in worn condition.

Food.--The pine siskin is a tree- and ground-foraging finch. Like the crossbill, it often hangs upside down when feeding in vegetation, but it is a more generalized feeder, not tied closely to cone feeding and hence independent of the varying extent of the cone crop.

The results of food habits analyses were summarized by W. L. McAtee (1926): "The food of the siskin is principally the seeds of coniferous trees, alder, birch, ragweed, and other weeds. About one-sixth of the total food is animal, consisting chiefly of caterpillars, plant lice, scale insects, and grasshoppers. No doubt the siskin pays, in the destruction of these pests, for the forest seeds it consumes."

Two decades later Dorothy Mierow (1946), having more published information to summarize, wrote:

They feed their young mainly on aphids and seem quite content with alder, birch, and willow seeds. As they wander farther south and over the plains, their main items of diet may become weed seeds. Farther east, seeds of sweet gum, maple, and elm, as well as buds and insects, form part of their diet. In California, where they seem to be most numerous, they often feed almost entirely on the seeds of eucalyptus, extracting them from the pods either on the trees or on the ground. They also seek after the sweet liquid in the eucalyptus flowers.

The following information elaborates on the taking of some of the items already mentioned. Also, in some measure, it indicates seasonal and geographical variation in food habits, plus mentioning some items taken that might not be readily identified in analysis of contents of digestive tracts.

In early April in Ohio, examination of a siskin revealed it had been feeding on flower buds of the slippery elm (Kemsies, 1948). In June in West Virginia, Maurice Brooks (1943) saw siskins avidly eating the coated carpels of young spruces. Mr. R. E. Mumford writes of seeing birds feeding on Jack pine cones (Pinus banksiana) during an invasion of Indiana during the winter of 1952-1953.

After Oct. 4, 1889, at Lake Umbagog, Maine, they were feeding exclusively on the seeds of birches (Brewster, 1938). John F. Ferry (1907) writes that, in winter in northeastern Illinois, "they were observed to feed industriously on coneless branches of pines and spruces. The object sought was probably the dry resinous aments of these conifers. They frequent patches of thistle and seed-bearing weeds and work very actively in perfect silence."

In South Carolina in the winter of 1896-97, a time of siskin abundance there, Arthur Wayne (1906) observed them "feeding on the seeds of sweet gum (Liquidamber styraciflua), and shortleaf pine (Pinus mitis)."

During a winter and spring when siskins were common at San Diego, Calif., F. F. Gander (1929b) noted that their food was almost entirely seeds of various species of eucalyptus, which they obtained from pods on the trees and also among fallen leaves.

In Flathead County, Mont., on Aug. 7, 1915, A. D. DuBois recorded pine siskins eating thistle seeds along the railway. "I watched one for some time. He would fly up to a thistle head and, clinging to it, sometimes nearly upside down, would pull out the cottony tufts one or two at a time, very dexterously and rather rapidly, working his bill along to the seed which he removed and then threw the fluff to the breeze, immediately working out another tuft. He pulled them part way out, a bunch at a time, afterward slipping them along until they came out one at a time or sometimes two." In North Dakota, O. A. Stevens wondered how the siskins got dandelion seeds. On investigation he found that they did not wait for the heads to open, but pulled off some of the bracts and took the seeds before they were fully ripe.

In two areas, on opposite sides of the continent, the siskin has reportedly done extensive damage to vegetable and flower gardens. From Independence Lake, British Columbia, T. and E. McCabe (1929) write regarding areas recently opened to farming:

None of us who have vegetable gardens have been spared by the siskins. Our own case is the most extreme, as we have attracted the species by means of amazingly effective salt and clay baits for banding purposes. It is now impossible to raise most vegetables except under wire. In rather long experience of gardens and their pests we have seen nothing to rival the instantaneous devastation which an unobtrusive flock of siskins can inflict, often before their presence in a garden has been noticed. Not once, but season after season, and time after time within the same season, we have seen long rows of seedling beets, chard, lettuce, radishes, and onions, cut neatly to the ground. . . . Peas and cole crops, as far as we know, are not taken, but we hear of the destruction of turnips. . . .

The farmers nearer the Fraser [River] suffer as much as we do and, in spite of being further from the mountains, more than most of our nearer neighbors. We know of one ranch where for years a barn door has been used as a deadfall, and the birds fed to hogs by the bucketfuls. In another case great numbers are shot, and as many as thirty-five have been picked up as the result of enfilading a row of vegetables with a single charge of shot. As the typical associations of the Canadian Zone are left behind, and the greater drouth and summer heat of the river flats approached, the nuisance decreases. From the immediate vicinity of Quesnel we hear a few scattered complaints of moderate losses, but a short distance southward, within touch of the long arm of Transition Zone conditions, which stretches so far up the valley, all knowledge of the trouble seems to disappear, though we do not know where it may recur.

In Maine, siskins occurred in thousands in the spring and summer of 1925. Forbush (1929) states that they "invaded gardens, stripped beets, beans and other plants of their leaves, and ate the blossoms of many flowering plants." A correspondent in Patten, Maine, wrote Forbush that he had seen "as many as a thousand birds on a half acre."

Both the insect foods and ways of obtaining these are varied. In Ohio during a "most unseasonable and heavy snow in early October, these little birds surrounded our houses and literally skimmed the outer walls of all insect life. From foundation to eaves they hunted in every nook and corner, capturing spiders, flies, cocoons. . ." (J. L. Parsons, 1906).

In February at Alameda, Calif., an oak (Quercus agrifolia) was swarming with siskins. F. N. Bassett (1923) noted that the birds were procuring their food from the lower surfaces of the leaves. Many leaves were afflicted with the gall of a saw-fly, Callirhytis bicornis. Bassett reports: "The galls were attached to the midrib or a lateral vein on the lower surfaces of the leaves. They were composed of leaf material, light green in color (lighter than the leaf), from two to four millimeters long and shaped somewhat like a miniature saddle, being depressed in the middle and rising to an apex at both ends. Each contained a minute milky-white grub and many close views revealed the birds 'shelling' the galls and devouring the contents exactly as a domestic canary shells its seeds."

In February at Berkeley, Calif., T. L. Rodgers (1937) writes about siskins feeding in Monterey cypress:

I was unable at first to determine by observation, exactly what the birds were eating, so I collected one hundred cypress tips, averaging three inches long and representative of places all over the side of a tree on which I watched many siskins foraging. Examination of the cypress tips showed many psocid-like insects, many scale insects, a few small green caterpillars, and many yellow larvae that were inside thin-walled cavities in enlarged green vegetative tips. There were few indications of broken-off vegetative tips, but some were damaged, which probably indicated that some of the yellow larvae had been torn from their chambers. The indication was quite definite that the siskins were taking only insect food.

Rodgers also saw a siskin picking aphids which it fed to a young bird just out of the nest. In April at Seattle, Wash., S. F. Rathburn recorded this observation: "I noticed that, when alighting on any older limb, the siskins would examine it closely until its extremity was reached, and this was particularly the case when any had the appearance of being dead. Then the bird would clip or break off the twig's end. I examined one of the twigs that fell and, in breaking it, I found deeply embedded within a fat grayish-green grub, evidently the larva of a twig-boring insect. This explained the siskins' actions."

The McCabes (1929) mention the attraction that salt and clay have for siskins. In an earlier article (1928) they state: "The attraction has always been some mineral food, relish, or medicament, natural or artificial. Ashes, deep blue clay from a cellar hole, salt, and newly-set Portland cement have all had their periods of favor." The habit has been noted in different seasons at widely separated points. Mierow (1946) made the general statement that a "necessary item in the siskin's diet, as well as in that of other boreal finches, is some kind of mineral salt." D. S. Farner (1952) reported this habit in Crater Lake National Park as follows: "Although to a much lesser extent, siskins display 'salt-feeding habits' similar to those of the Red Crossbills. Especially during the summer of 1951 it was possible to observe siskins pecking at the powdery crusts on the andesite rocks."

In the first half of March 1941, between Saranac Lake and Tupper Lake, N.Y., the road had been treated with a mixture of sand and calcium chloride--the latter apparently added as a binder for the former. G. M. Mead (1942) quotes an observer as follows:

For several days great numbers of White-winged Crossbills and small numbers of Red Crossbills and Pine Siskins settled on the road to eat the salt. The roadbed was covered with them and it was almost impossible to scare them away even by using the horn. They appeared to be too sick to rise and even though motorists drove slowly they were killed in great numbers. The surface of the snow-covered road was actually reddened by the blood and feathers of the birds. My estimate is that there were at least a thousand birds killed.

From Rutherglen, Ontario, it is clear from the following observations for the winter of 1947-48 by Louise de Kiriline Lawrence that salt in some form is a real desideratum of siskins. She writes: "At this time, the birds were encountered chiefly on the highway where they assembled in dense flocks, eating gravel mixed with chloride. Soon after sun-up they began to appear in these places with their numbers reaching a peak around midday, followed by a slow decline until, just before sunset, the last flock flew away to roost. Many of these birds apparently travelled considerable distances to these cherished feeding places; I saw birds winging their way to and from the highway from the woods at least a mile away. When disturbed, the birds swung off the road as of one accord, amid excited twitter, to alight in the trees alongside and there continue their feeding on the seeds of the evergreens, or on the buds of the white birches and aspen trees, with the siskins showing particular liking for the seeds of the alder-bushes. The siskins were a gregarious lot, associating freely with all the other finches, especially the Goldfinches and the Red Crossbills.

"The pine siskins were first attracted to my feeding place under the pines, a little off the highway, by the coal ash pile. One day they dropped down from the surrounding trees by the dozens. I counted 92 before I got too mixed up by their numbers, all clustered into a little space 10 inches by 10 inches in front of my window. They ate the ash-dusted snow mixed with slop water. On an old cedar stump I kept a block of salt. From rain and snow and the humidity of the air, the salt had saturated the stump and this saltlick became hereafter the number one attraction. The birds crawled over the stump and picked the salt crystals from the block itself as well as from the top and the underparts of the stump, where the deposition of crystals was richest, and from the gravel around it, where the snow had been melted away by the salt. I put baited traps near the saltlick, hoping for some good banding, but not until I changed the bait to dried cedar seeds did my banding luck turn. These seeds proved irresistible to the siskins and when my supply ran out I put small dishes of water in the traps with the same excellent results. Thus, from January 7 to May 29, I banded 337 pine siskins."

Siskins can be attracted to feeding stations by millet seed and by chaff, and Forbush (1929) states that they are "extremely fond of cracked butternuts." They eat many of the vegetable foods commonly used at feeding or banding stations, and eat suet occasionally. In winter at Leominster, Mass., E. R. Davis (1926) notes that whenever "an Evening Grosbeak came to the feeding-shelf and began cracking the seeds, he would be surrounded by several of the siskins. As he cracked the seeds, some particles of the kernel would scatter from his beak, and immediately the siskins would rush in and gobble them up. This act was not much relished by the Grosbeaks and they would often show their displeasure by a vicious peck at the intruder. . . ."

Dishes of water, for drinking and bathing, have been used to bait siskins into traps for banding. At Sioux City, Iowa, a basin of water was placed under a nesting tree and both parent siskins came to drink and bathe (Hayward and Stephens, 1914). In March at Berkeley, Calif., T. L. Rodgers (1937) observed:

Several times, I saw siskins approach [eucalyptus] blossoms from above, lean over and reach into them. I had supposed they were after insects attracted by the flowers, but twice I noticed that after reaching into the blossoms, they raised their heads after the manner of a chicken drinking. I gathered a large bunch of the blossoms and in every one examined found several drops of clear sweet liquid, with only a slight eucalyptus flavor. Later, I saw more siskins drinking from flowers, also a junco.

At Macon, Ga., in late December, a siskin was observed at borings made by a yellow-bellied sapsucker in the trunk of a sweet gum. The sapsucker chased it away (H. L. Batts, 1953).

Field marks.--It is somewhat difficult to distinguish at a distance between the pine siskin, the goldfinches, and the redpolls. Not only do these various birds mingle in flocks, but their size, manner of flight, call notes, and general habits, are all quite similar. The siskin, however, is characterized in all seasons by its dusky-streaked plumage (on grayish brown base above, more or less whitish or buffy below) two light wing bars, and, usually, considerable yellow on the basal portions of its wing and tail flight feathers. It has no red on its crown or black on its throat as the redpolls do. Siskins in juvenal plumage have the adult pattern but, for some time after they first fly, they are readily distinguished from their elders at close range by the worn plumage of the latter, the young being much buffier, their underparts often tinged with pale yellow, and their overall appearance lighter. Our siskin at any age is fairly similar in color and pattern to the female and juvenal Spinus spinus, the siskin of the Old World--a species in which the adult male is redpoll-like in having a crown patch (which is black in the siskin) and a blackish chin.

Voice.--Various utterances frequently are compared with those of the goldfinch, redpolls, and canary. Call notes are given in chorus, especially when the birds alight or rest. Descriptive words commonly used by describers of siskin call notes are: weak, thin, lispy, buzzy, wheezy, and churring. In general their calls are more husky than those of the American goldfinch.

Ralph Hoffmann (1904) describes the common call notes as "chee-ee given in a husky tone; when flying it utters a note like the syllables tit-i-tit. Another very sweet call, often given by a single bird to call back the flock, is identical with a note of the American Goldfinch." In winter at Anniston, Ala., R. H. Dean (1923) observes that, when siskins took flight, their utterances were tit-i-te, tit-i-te, several times in succession; sometimes notes were a smoother see-a-wee. On March 22, a new note was recorded, z-z-z-z-z (a prolonged z), weak, as are all the notes, but rather harsh. The z notes seem to be part of the song, "a weak prolonged chittering performance interspersed with the louder z-z-z-z notes." A. A. Saunders (1935) points out that the siskin has an "undulatory flight, calling tit-a-tit with each undulation." He also mentions a "husky but sweet swi-sieee, slurring upward at the end, much like the Goldfinch's similar note, except for the huskiness. He says that the siskin's song is uttered in choruses and that mixed choruses are heard when goldfinches and siskins flock together. The latter's song much resembles the former's, being a "long-continued series of notes, groups of two-note phrases, or single notes and long trills." The quality is "husky, and the trills fricative and like a loud long whisper."

From Rutherglen, Ontario, Louise de Kiriline Lawrence sends this observation: "From this day [January 29], the Pine Siskin's singing became common all over the woods. It was particularly intensive during the morning and early forenoon. The birds sang from perches, sometimes from the top of a bush along the road, at other times from the highest twig of the tallest tree. Their song included some of their common notes, which seemed to serve as punctuations between the more elaborate sentences and a 'vireo' song, very like that of the Purple Finch, only with the performance in keeping with the Siskin's smaller size. A 'churry' (not 'burry') note was also interpolated often in the singing, so like that of the Evening Grosbeak that I several times mistakenly thought the Grosbeaks were present unseen amongst the trees. The weather had no effect whatever on the Siskins' vocal ardor, be the day dull and mild, or cold and clear with the temperature far below zero."

From Camrose, Alberta, F. L. Farley writes me as follows of a siskin found injured on November 29 and kept in a cage: "It is now more than two months since we have had him and we are all surprised with his musical ability. Between daylight and noon every day he sings just as continuously as most of the tame canaries, and the most interesting thing we have learned is that he combines the well known notes of Goldfinch and Redpoll and the rich ones of the tame Canary. Then, in between these songs come the nasal squeez or issch so diagnostic of the Siskin in its wild state. As I write now, he is singing quite steadily, and in between songs he gives the Canary e-r-e. His songs are on a low scale and cannot be heard more than a third of the distance that a tame Canary's voice carries."

Enemies.--Friedmann (1963) writes: "Generally, the pine siskin is ecologically allopatric with the brown-headed cowbird, a fact which effectively protects it from the attentions of the parasite. However, there are places where the two species overlap and here the siskin is occasionally imposed upon. Eleven such instances have come to my notice, distributed among the following states: Iowa, Kansas, Nebraska, South Dakota; and in Canada: Ontario and British Columbia." To these may be added N. J. Ilnicky's (1963) observations of a pair of siskins feeding a newly fledged cowbird in Marquette, Michigan, on July 11, 1962.

*Original Source: Bent, Arthur Cleveland and collaborators (compiled and edited by Oliver L. Austin, Jr.). 1968. Smithsonian Institution United States National Museum Bulletin 237 (Part 1): 424-447. United States Government Printing Office

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