Bay Area Birds: An irruption of birds

By Charlie Frisk
Correspondent

Irruptions are events that birders, those who feed birds and stores that sell bird seed look forward to.

An irruption occurs when a species migrates to an area in large numbers based on food supply rather than seasonal changes.  

Irruptions occur irregularly.

Sometimes just a few years may go by between irruptions for a certain species, while for others it could be decades.    

Seed-eating birds will irrupt into other areas during years of poor seed production.

The largest irruptions occur when a high-seed production year resulting in a higher-bird population is followed by a poor seed production year.

Seed-eating birds that are known for irruptions in this area are pine and evening grosbeaks, red breasted nuthatch, pine siskins, common and hoary redpolls as well as red and white winged crossbills.  

This winter, the Green Bay area is experiencing a major irruption of common redpolls and a smaller number of pine siskins.

Siskins and redpolls are finches and are in the same genus as the eastern goldfinch.  Goldfinches are found in the area every winter, but this winter the number of common redpolls far exceeds the goldfinches at the feeders. 

Common redpoll

The common redpoll is an attractive little bird, and as the name indicates both the male and female have a red cap on top of their head, with the males having a rose flush on their breast.  

Common redpolls and pine siskins prefer Niger (also spelled Nyjer and also known as thistle) and black oil sunflower seed.

If you are feeding birds and the redpolls have found your feeders, the seed consumption at your feeders will have increased dramatically. 

Mike Steffel, owner of Wild About Birds in Green Bay, said his seed sales have gone up about 40% since the redpolls and siskins arrived.   

Even when there are plenty of spots open on the feeders, many of the redpolls prefer to feed on the ground.

I always sprinkle a little Niger and sunflower on the ground for them.

Except in irruption years, the common redpoll spends winters in the boreal forests, composed of pines, spruces and larches, of Canada and the northern United States.  During irruption years, they can be found as far south as Arkansas and Texas.  

The common redpoll nests in the boreal forest, whereas its close relative, the hoary redpoll, nests in the Arctic tundra.

The hoary is lighter colored in general and has unstreaked undertail coverts and less streaking on the sides compared to the common.

The differences are more pronounced in males than in females.

Occasionally, hoary redpolls will be mixed in with commons during an irruption year, but I personally have never seen one.

Pine siskins

Pine siskins have a very thin, pointed beak with a streaked breast.

The males have yellow wing-bars and the females white wing-bars.  

This year is also an irruption year for white-winged crossbills.

On one recent morning, my wife and I were watching our feeders, and a flock of 30-40 birds landed in a tall white spruce in our backyard.

I could tell they were larger than the redpolls, and when I got them in my binoculars I realized they were white-winged crossbills, a thrilling new life-bird for me.  

We were both amazed.

I had always expected that if I were to see white-winged crossbills it would be somewhere up north in a conifer forest and certainly not in my backyard in Green Bay.

Red and white-winged crossbills have crossed bills to enable them to extract the seeds from conifer cones, which make up almost their entire diet.

The crossbills we were watching fed on the white spruce cones for about ten minutes before departing.

If you see a flock of birds land in the top of a conifer and start picking at the cones, get your binoculars on them, it is a good chance that they are white-winged crossbills.

The females are sort of a tawny yellow, while the males are pinkish red.

Both sexes have two very distinctive white wing bars on the forward part of the wing.  

Crossbills rarely come into bird feeders, but will occasionally feed on sunflower seeds.  

Raptors (birds of prey) also experience irruption years when their prey animals are on the low end of their cycle.

Rough-legged hawks, northern goshawks, snowy, short-eared and great gray owls are known to irrupt periodically.  

This winter has been particularly good for rough-legged hawk sightings, and a few people are reporting snowy owls.

I will cover raptor irruptions in more detail in another column.  

This is a great year to see common redpolls and pine siskins.

If you don’t feed birds yourself, visit a friend’s place where they do and you might see these special winter visitors.  

Bay Area Birds is a monthly column written by local ornithology enthusiast Charlie Frisk.