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THOSE BROWN PURPLE FINCHES

Although Purple Finches don't breed anywhere near Hilton Pond Center, they're certainly no strangers to our feeders. Most winters these migrants from up north make their way to the Carolina Piedmont, undoubtedly drawn by food unhidden by snow that often blankets the woods and fields of their nesting grounds in Canada, New England, and the Great Lakes states. Indeed, Purple Finches are among the "money birds" that bring revenue to feed stores and wild bird emporia across the southern U.S.; when Purple Finches arrive, cash registers start ringing as backyard birders dig deep to buy 50-pound bags of sunflower seed. Purple Finches typically flock to our feeders at Hilton Pond from January through March, chowing down on our high-energy offerings and often entering traps we've baited with black oilseed. So just how common are Purple Finches at the Center? In the 23 years since we captured our first one on 9 January 1983, we've banded 6,964 Purple Finches--but not all of them have been purple.

All text, charts & photos © Hilton Pond Center

Indeed, about 75% of nearly 7,000 Purple Finches banded at Hilton Pond Center have been brown--not purple--which quickly brings us to our real reason for devoting our current photo essay to this species: Despite continuing reports we read on-line, receive by phone, or get when bumping into acquaintances in the supermarket checkout line, an abundance of brown Purple Finches does NOT mean there's a scarcity of MALES. In fact, saying you have something like "three male and seven female Purple Finches" at your feeder is more than likely incorrect. Raspberry-colored Purple Finches outside your window are indeed adult males, but the brown ones could be adult females, young females, OR young males; i.e., in Purple Finches it takes two years for males to get their full purple plumage.

It's likewise not safe to say that birds with a pink wash or gold rump (above) are young males because old females occasionally develop these colors. Even in hand it's essentially impossible in winter to tell whether a brown Purple Finch is a female or a young male, although it's very probable birds with pointed tail feathers (below left) are young birds, while those with broader and truncate, rounded, or "less-pointy" rectrices are adults (adult male below right). In any case, rectrix shape is not something one is liable to use in ageing or sexing a bird at the feeder, so in winter you're always safer--and can avoid being be outright wrong--by saying ALL brown Purple Finches are of unknown sex and age.

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The finches themselves, of course, know what sex they are and are probably quite adept at identifying individual birds within a population. However, even though we humans can recognize thousands of different people faces, it's difficult for us to comprehend just what visual, audible, behavioral, or even telepathic cues a Purple Finch may use to differentiate females from immature males or one particular bird from the next. Backyard enthusiasts can single out an occasional bird with an unusual morphological or behavioral trait, but for the most part all Purple Finches--AKA Carpodacus purpureus--look pretty much alike to us humans.

Since we actually band our Purple Finches at Hilton Pond, it IS possible for us to differentiate some individuals--although we have to recapture them to do so. That's how we first learned that pink-rumped birds (above)--which we once thought all were young males--sometimes looked the same in subsequent years, meaning they must actually be females. Banding is also how we found out Purple Finches are our winter species most affected by ticks (below right); this winter in particular we've had numerous Purple Finches with at least one ectoparasite--always in the head region (see An Epidemic Of Bird Ticks?). And banding also helped us understand that migration in Purple Finches is probably facultative rather than obligate.

As the word implies, "obligate" migration means a species is "obligated" to depart a nesting area and fly to different wintering grounds. For example, Ruby-throated Hummingbirds bail out each autumn, deserting virtually all their breeding range in the eastern U.S. and southern Canada. They're "obligated" to do so, being unable to survive northern winters due to lack of flower nectar and insects and/or because the weather is too cold; the same can be said of many warbler species that breed in North America and "winter" in the Neotropics.

"Facultative" migrants, however, may or may not migrate--a behavior that probably depends not on ambient temperatures but on whether enough food is available on the breeding grounds in a given winter. We suspect cold-hardy Purple Finches are facultative migrants because we get them in variable concentrations from year to year, and some winters we get almost none at all. Rather than feeding on nectar flowers--which die EVERY winter in northern latitudes--Purple Finches rely primarily on berries and seeds, whose abundance may vary greatly from winter to winter. If the seed crop is plentiful up north, the winter finches stay; if it fails, these birds are far more likely to wander southward in search of food.

Click HERE for a larger version of the chart above

Unfortunately, we haven't been able to compare winter food availability in Purple Finch (PUFI) breeding areas to the prevalence of PUFI on their wintering grounds at Hilton Pond Center, but the chart above still reveals some interesting things about our local populations:

Based on all the above, we conclude Purple Finches are indeed facultative migrants. In our experience at Hilton Pond Center, PUFI begin to trickle in as early as late December, reaching a peak in February or early March; this may indicate food resources on their breeding grounds are gradually being depleted--or covered by snow--such that seed- and berry-eaters are forced to move southward. The same may be true for American Goldfinches--our third most common banded bird at the Center.

One thing we DON'T yet understand is whether there's any real difference in migration timing between male and female PUFI. Again, that's because the only newly banded Purple Finches for which we KNOW the sex are red adult males (above). We'll have to recapture a lot more banded Purple Finches in subsequent years to conclusively determine whether Hilton Pond's brown ones (below) are females or actually young males that haven't yet acquired their distinctive raspberry plumage.

All text, charts & photos © Hilton Pond Center

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RECENT GIFTS

Thanks to the following fine folks for recent gifts in support of Hilton Pond Center for Piedmont Natural History and/or Operation RubyThroat: The Hummingbird Project.

James Associates (MacGPS Pro X)
Margaret Zircher

Be sure to scroll down for an account of all birds banded or recaptured during the week, plus other nature notes of interest.

"This Week at Hilton Pond" is written & photographed
by Bill Hilton Jr., executive director of
Hilton Pond Center for Piedmont Natural History.

You may wish to consult our Index of all nature topics covered since February 2000. You can also use the on-line Search Engine at the bottom of this page.

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