Wednesday, April 14, 2010

What a beak...the Evening Grosbeak

Here we have a rather uncommon bird that many of you may not have experienced yet. But one thing is almost for certain: if you see one, you will see many more! Moving around often in large flocks, the evening grosbeak (Coccothraustes vespertinus) can fill your surrounding trees with a loud chorus and also drain your large birdfeeders of sunflower seeds in a hurry.
About 140 years ago, English-speaking settlers in the foothills of the Rocky Mountains came across a beautiful big-beaked bird that appeared mysteriously from somewhere in the distant west. They named it evening grosbeak in the mistaken belief that it came out of the woods to sing only after sundown. The species today has expanded its range---prior to 1890, they were unknown east of the Great Lakes, whereas today they continue to expand their breeding range throughout the East. Thus not until recent times (historically speaking) have they even been known to exist to white settlers. The modern day abundance of sunflower seeds at feeding stations is one of the keys to its range expansion as the seeds available have extended the chances of them being able to survive the winters in areas their native wintering seeds (primarily seeds from the cones of spruce, balsam fir, and pine trees) never existed!

The evening grosbeak is considered a very common bird…if you are lucky enough to have them around. However, they are very spotty in their distribution and while one area might be overwhelmed with dozens of them the next areas will not have a single specimen. They are an erratic migrant in winter as the occurrence of their flocks is unpredictable. They are large, gregarious, nomadic finches that travel in raucous flocks. During the winter, evening grosbeaks are irregularly common, sometimes appearing in large flocks at feeders where they can devour huge amounts of sunflower seeds. I can’t describe the amazing sense you experience when getting the opportunity to stand outside and listen to a flock of 30 or 40 of them all chirping! The chorus of chatter they create is absolutely lovely!
A fascinating feature about this bird is of course its beak. The evening grosbeak's bill is bone color during winter, but it undergoes a dramatic change in pigmentation in early spring. Its new color matches precisely the green of fresh deciduous buds and leaves and also the new needles that will tip the spruce boughs around the site where the bird's nest will be built a few weeks thereafter. The evening grosbeak conceals its body in the trees and in order to see lifts only its head and bill, which looks like a young green spruce or balsam cone. This is a terrific example of protection through appropriate coloration!

Certainly no farmer will wish to take away from them the weed seeds they devour. A grosbeak getting all its daily energy from budworm larvae would eat 1000 a day. These birds crowd into budworm infested areas to breed and raise young, then move elsewhere when the infestation declines. Because of its appetite for this destructive pest, the evening grosbeak is one of our most beneficial birds! So while they are not as common as our summer visitors, the black-headed grosbeaks, they certainly are a joy to experience if you are so lucky to have them at your feeders during their times passing here in the area!


  1. That is some really interesting information, Alan! I learned a lot. I will show this post to my kids, who also love birds. They will be clamoring for a field trip to your place to come see them, though!

  2. Thanks for reading Jennifer!

    Now we've got the Band-tailed Pigeons guarding our property in force. I think we have a nesting pair of Red-brested Sapsuckers as well since I'm seeing two of them together almost all of the time!