Bird Profile

Pine Siskin

Siskins show up by the dozen in some winters and are absent for three years running. The winters they arrive are also the winters feeder disease outbreaks make the news.

The Pine Siskin (Spinus pinus) is a small brown finch, about 5 inches (13 cm) long and heavily streaked from throat to flanks, with a thin sharply pointed bill and a flash of yellow in the wing and tail. It is a goldfinch relative in a brown coat, and in most yards it is either absent entirely or present in noisy dozens.

Two things make siskins worth understanding. The first is that they are irruptive, so their appearance depends on a seed crop failure a thousand miles north of you. The second is less pleasant: winters with big siskin flights are the winters feeder salmonella outbreaks turn up in the news.

This profile covers how to separate a siskin from the streaky brown finches it resembles, what drives an irruption, the disease risk in detail, the feeders and seed that work, and how siskins behave once they take over a yard.

How to identify a Pine Siskin#

Overall: a small, slim, restless finch with fine dark streaking over a brown-and-buff body, a notched tail, and a thin, straight, sharply pointed bill. Sexes look alike, though males average more yellow.

The yellow. Siskins show a yellow wash along the flight feather edges, forming a thin yellow line down the folded wing, plus yellow at the base of the tail that shows best in flight. Some birds are bright; some show almost none. It is a confirming mark, not a first one.

The bill is the reliable mark. Every common confusion species has a heavier bill. A siskin bill looks like it was sharpened.

Voice. The giveaway is a rising, buzzy zzzree-ee-eep like a zipper being pulled, mixed into a chattering, twittering flock noise. Once you know that call, you will find siskins overhead that you would never have spotted.

The four birds people confuse with siskins#

Female House Finches are the source of most misidentifications, because size and general brownness match. Bill shape settles it in two seconds.

What an irruption actually is#

Siskins breed across the boreal forest and the western mountains, where they live on the seeds of spruce, pine, hemlock, alder and birch. Those trees do not produce evenly. Whole regions have a heavy cone year and then a near-total failure, and when the failure is widespread the birds have to leave.

That is an irruption: a mass movement driven by food, not by cold or by calendar. It sends siskins into the Midwest, the Southeast, the desert Southwest and occasionally the Gulf Coast, in numbers that vary by a factor of a hundred from year to year.

Consequences worth knowing:

• Siskin winters are unpredictable in advance. Regional forecasts based on northern seed crops exist and are often right, but nobody can tell you in September whether your yard gets siskins.
• Flocks are mobile all winter. Forty birds can occupy your feeders for a week and then disappear for a month.
• Some irrupting birds do not go home. Siskins occasionally breed far south of their normal range in the summer after a big flight.

Salmonella and siskins#

This is the part that matters most. Pine Siskin irruptions are strongly associated with salmonella outbreaks at bird feeders, and in big flight years those outbreaks have killed large numbers of siskins across whole states and provinces, particularly in the West.

The reasons are behavioral. Siskins feed in tight flocks, crowd onto trays and perches, feed on spilled seed on the ground, and travel long distances, which moves bacteria between yards. Droppings on a feeder tray contaminate the seed, the next bird picks it up, and a feeder becomes a transmission point rather than a food source.

Signs of a sick bird: fluffed up and unusually still, eyes half closed, sitting on the ground or on the feeder for long periods, reluctant to fly when you approach. Siskins are naturally tame, so tameness alone is not a symptom; lethargy plus fluffed feathers is.

Prevention in a siskin winter is simple and unglamorous: wash feeders on a fixed schedule rather than when they look dirty, prefer tube and mesh feeders where birds cannot stand in the seed, and move feeders occasionally so droppings do not build up in one spot. Method in how to clean a bird feeder, dilutions in safe disinfectants for feeders, and frequency in how often to clean bird feeders.

Food and feeders that work#

Siskins are small-seed specialists with a bill built for prying seeds out of cones and catkins.

• Nyjer in a nyjer or mesh finch feeder is the standard, and a mesh sock or tube lets many birds feed at once.
• Sunflower hearts are taken just as readily and are cheaper per calorie. Whole black oil sunflower is workable, though siskins are slower at shelling it than a goldfinch.
• Suet crumbs and fine chips get picked at, especially in cold snaps.
• In the yard, they take seed from birch and alder catkins, sweetgum balls, coneflowers and unmown weeds. Leaving seedheads standing through winter feeds them for free.

Siskins also crave minerals and will come to grit, wood ash and roadside salt, which is one of the few times you will see them on the ground away from a feeder.

Behavior worth knowing#

Siskins are aggressive for their size. A bird half the weight of a House Finch will spread its wings and tail, lunge, and hold a feeding port against much larger birds.

They are also strikingly unafraid of people. A flock will keep feeding while you stand at arm's length or refill the feeder next to them. That tameness is charming and is also part of why sick birds are noticed at feeders more often than in the wild.

In cold weather siskins can pack seed into the crop, an expandable pouch in the throat, and digest it overnight. They can raise their metabolic rate substantially above what a similar-sized songbird would sustain, which is part of how they survive nights well below zero. Cold-weather feeding generally is covered in winter bird feeding.

Nesting#

Siskin nesting is loose and opportunistic, and it happens wherever the birds happen to be in spring rather than in a fixed territory. Nests are shallow cups of twigs, grass and rootlets, lined with fur, feathers and moss, placed well out on a horizontal conifer branch and usually hidden by dense needles.

Pairs often nest in loose colonies, sometimes several nests in one tree, which is unusual among finches. The female incubates and is fed on the nest by the male. Broods can appear surprisingly early, sometimes while snow is still on the ground.

If a large irruption puts thousands of birds far south in winter, some of them stay and nest there in spring, then vanish north again the following year.

Population and conservation#

Pine Siskins are still numerous, but long-term North American survey data has shown a substantial decline over recent decades, and the species is often cited among the boreal forest birds losing ground. Boom-and-bust numbers make trends hard to read from any one yard, which is why counts collected over many winters matter more than what you see in a single season.

Disease is one pressure feeders can genuinely influence. Salmonella deaths at feeders are a real component of siskin mortality in irruption years, and clean feeding stations reduce it.

What to do in a siskin winter#

• Put up a second finch feeder as soon as the flock arrives, and set it well away from the first.
• Buy nyjer in quantities you will use in about a month; it goes rancid fast and birds reject it before you can smell it.
• Clean feeders every week while the flock is present, fully dismantled and dried.
• Rake the ground under the feeders and move the feeding station a few feet every few weeks.
• Watch the flock for a bird that sits fluffed and does not flush, and act on it the same day.