Pine Siskin: the irruption bird, and the disease risk that follows it

The short answer

• A siskin is a small, heavily streaked finch with a thin, sharply pointed bill and yellow flashes in the wing and tail. The bill shape separates it from every other feeder finch.
• Numbers swing wildly between winters because siskins follow the northern conifer seed crop, not the weather. A yard can go from zero to sixty in a week.
• Nyjer and sunflower hearts are the top two foods, taken from a nyjer tube, a standard tube or a tray.
• Big siskin winters are when salmonellosis outbreaks at feeders happen. Crowded perches, wet seed and droppings on a tray are the mechanism.
• If you find a fluffed, sluggish bird that will not fly, take every feeder down, clean everything and leave the station empty for at least two weeks.

Some winters there are none. Then one November a flock drops into the birches, and by the following week you are refilling a nyjer feeder every second day for forty small streaky birds that will not move when you walk up to it. That is a Pine Siskin winter, and it comes with a job attached.

Bill first, then the yellow#

At a glance a siskin looks like several other things: a female House Finch, a winter-plumage American Goldfinch, a redpoll, or a sparrow on a tube feeder. One feature ends the argument.

• The bill is thin, straight and pointed. Every other finch at your feeder has a short, deep, blunt cone. A siskin's is a needle, because its living is made prying seed out of half-open spruce and alder cones rather than cracking hulls in the open.
• Yellow in the wing and tail. A yellow bar at the base of the flight feathers and yellow edges along the tail. Some birds show it constantly, some only when they stretch a wing or take off. Absence does not rule a siskin out, presence rules everything else out.
• Streaking everywhere. Fine dark streaks over the whole underside and back, not just the breast. A female House Finch is blurrier, browner and plainer on the back.
• Size and shape. About 14 g, so goldfinch-sized, with a notched tail and a long-winged look.

At the feeder: tame, dense and unexpectedly ferocious#

Siskins are the least shy finch most people will ever have in the yard. They frequently keep feeding while you refill the next feeder, and a flock will let you stand within a few feet. Do not read that as calm. Within the flock they squabble constantly: wings spread and drooped, bill gaping, lunging at neighbors over a port they are not even using. A siskin will hold a perch against a bird twice its weight.

Practical consequences of how they feed:

• They stay. Chickadees take a seed and leave. A siskin sits at a port and eats there, sometimes for fifteen or twenty minutes. There is no caching at all.
• They pack in. Every port occupied, birds hanging off the mesh between ports, more on the ground under it. This is the single fact that drives everything in the next section.
• Flock size. Ten to sixty is ordinary in an irruption year, and larger flocks happen. Our data rates them at the top of the flocking scale alongside goldfinches.
• Time of day. All day. Siskins feed from first light to dusk with no strong midday drop, which in a short northern winter day means near-continuous occupation of your feeder.
• They travel with goldfinches. Scan any mid-winter goldfinch flock in an irruption year bird by bird. Siskins mix in and are easy to miss when the flock is all facing away.

Salmonellosis: the part nobody wants to read#

Songbird salmonellosis is caused by Salmonella bacteria spread through droppings. Birds pick it up from contaminated seed and surfaces, and it can kill quickly. Outbreaks in North America are repeatedly linked to winters with large siskin movements, and during the widely reported West Coast outbreak of recent years state and provincial wildlife agencies from California through British Columbia asked people to take feeders down entirely for a period.

The mechanism is not mysterious. Put forty birds on one feeder for eight hours a day, add droppings landing on a tray and on the seed below, add damp weather, and you have built a transmission point. A tube feeder with a tray, or a platform, is the highest-risk design because seed and droppings share a horizontal surface.

In a normal winter, clean feeders every two weeks. In a siskin winter, do this instead:

That last line is the cheapest intervention available. Two more feeders 20 ft apart cuts the density on each one without reducing the food. The full routine is in how to clean a bird feeder, and the wider disease picture, including finch eye disease and avian influenza, is in bird diseases at feeders.

What to offer#

1. Hearts Top
2. Nyjer Top
3. Black oil Yes

Nyjer and sunflower hearts sit at the top together. In a siskin year there is a real argument for running hearts as the main food and nyjer as the second: hearts leave no hulls, so nothing wet accumulates on the ground, and they suit chickadees and goldfinches equally. Nyjer costs more per pound and siskins go through it fast, so keep the quantity you store to about six weeks of use. Details on both in nyjer seed and sunflower hearts.

Feeders they use: a nyjer tube or mesh feeder first, a standard sunflower tube second, a tray third. A mesh nyjer feeder lets more birds feed at once than a ported tube, which is good for the birds and bad for hygiene, so pair it with the shorter cleaning cycle above. Skip suet, peanuts, corn and mealworms: siskins barely register them.

When your yard gets none#

Before you change anything, check whether anyone in your county is reporting them. Irruption is a continental event and the honest answer is usually that the birds are 600 miles north of you eating spruce seed.

If they are around and you have none, the usual causes are these. Your nyjer is stale, which is the commonest single fault: nyjer is a small oily seed that dries out and loses its appeal within a few months, and birds will refuse an apparently full feeder of it. Buy small, store cool, and if a feeder has sat untouched for three weeks, dump it. Second, your ports are the wrong size: sunflower ports let nyjer run out onto the ground, and nyjer slits jam with sunflower. Third, your feeder is in the open with nothing to drop into. Siskins stage in a tree first. Fourth, and easily missed, the flock is present and feeding on natural seed: a heavy local birch, alder or sweetgum crop will hold them off feeders entirely until it is gone. For a wider diagnosis, work through no birds at my feeder.

The year in outline#

Siskins nest in conifer forest across Canada, the western mountains and the northern tier of the United States, sometimes very early in the year and sometimes not at all in a given area. Autumn movement begins in October and is finished by December. If they are coming to you, they will be there by the end of November in most years.

Numbers hold through midwinter, then late February and March bring the strangest part of the cycle: birds that wintered further south move back north, and a yard that was quiet all winter can fill with siskins during a mid-March cold snap. Keep feeding into April. Spring feeding matters more for irruptive finches than for almost anything else, and winter feeding covers the cold-weather setup they arrive into.

Frequently asked questions#

How do I tell a Pine Siskin from a female House Finch or a winter goldfinch?

Look at the bill. A siskin's is thin, straight and needle-sharp, built for prying seed out of a conifer cone. A House Finch or goldfinch bill is short, deep and blunt, built for cracking. Then look for yellow: siskins show a yellow flash at the base of the flight feathers and along the tail edges, most obvious when the bird stretches or flies. Streaking is also finer and covers more of the body than on a female House Finch.

Why do Pine Siskins show up some winters and not others?

They are irruptive. Siskins live on conifer, birch and alder seed, and those crops fail across huge regions in some years and are heavy in others. When the northern crop fails, siskins move south in enormous, unpredictable flocks and pour into feeders far outside their usual winter range. When the crop is good they stay north and your feeder gets none. Neither outcome tells you anything about your seed or your setup.

Are Pine Siskins a disease risk at bird feeders?

The birds are not the problem, the crowding is. Siskins feed shoulder to shoulder in large flocks for long periods, which means many birds contacting the same perches and the same seed, and droppings landing where other birds feed. Salmonellosis outbreaks in North America are repeatedly associated with big siskin winters, and wildlife agencies on the West Coast have asked people to take feeders down during them. Clean more often than usual, and act immediately on sick birds.

What does a sick siskin look like?

Fluffed up to twice its normal apparent size, sitting still on the ground or on a perch long after the flock has moved, eyes half closed, slow or unwilling to fly, sometimes with seed stuck around the bill. A healthy siskin is never approachable-slow in that way, even though the species is famously tame. One bird like that is enough reason to shut the station down.

Do Pine Siskins eat sunflower?

Yes. Sunflower hearts rate as high as nyjer for them, and they will take black oil sunflower in the shell too, though the fine bill makes hulling slower than it is for a House Finch. Hearts have a practical advantage in a siskin winter: no hulls piling up wet under the feeder, which is one less place for contamination to sit.

Will siskins empty my nyjer feeder?

Quickly. A flock of 30 to 40 birds feeding through short winter days can clear a 24 oz nyjer tube in two to three days, and the same flock will do it again the following week. Budget for it, buy nyjer in a quantity you will use inside about six weeks so it does not go stale, and store it cool and dry.

Sources and further reading

1. Pine Siskin Cornell Lab of Ornithology, All About Birds Identification, measurements, diet and irruptive movements
2. Sick Birds and Bird Diseases Cornell Lab of Ornithology, Project FeederWatch Signs of illness at feeders and what to do about them
3. National Wildlife Health Center US Geological Survey Wildlife disease surveillance including songbird salmonellosis
4. Pine Siskin National Audubon Society Guide to North American Birds Range and seasonal movement