Hornemann’s Hoary Redpoll

Posted by Mark Andrew Conboy

It’s no secret that QUBS is a great place for birds and birders alike. Enthusiastic birders visit Opinicon Road every spring to search for species that are at the northern edge of their breeding ranges such as Yellow-billed Cuckoo (Coccyzus americanus), Red-bellied Woodpecker (Melanerpes carolinus), Blue-gray Gnatcatcher (Polioptila caerulea), Yellow-throated Vireo (Vireo flavifrons),

A female Hornemann’s Hoary Redpoll (right) and a female Southern Common Redpoll (left) at Ironwood Cottage on February 9, 2011. Some of the key field marks are visible in this photo: generally whiter plumage (compared to the Common Redpoll), diffuse streaking on sides, nearly immaculate undertail coverts and a robust head and neck. Photo: Philina English. Please click on photo for larger version

Golden-winged Warbler (Vermivora chrysoptera), Prairie Warbler (Dendroica discolor), Cerulean Warbler (D. cerulea), and Louisiana Waterthrush (Parkesia motacilla). QUBS has also been a hub of avian research for decades, especially for species like Tree Swallow (Tachycineta bicolor), Black-capped Chickadee (Poecile atricapillus), Golden-winged Warbler, Yellow Warbler (D. petechia), Cerulean Warbler, American Redstart (Setophaga ruticilla) and Red-winged Blackbird (Agelaius phoeniceus).
Though the breeding season provides the best birding and is the busiest research season, occasionally interesting and unusual birds show up at QUBS in the winter. This year we’ve had our fair share of notable species including an unseasonable Winter Wren (Troglodytes hiemalis) and a juvenile Golden Eagle (Aquila chrysaetos). But the bird that has attracted the most attention is a Hornemann’s Hoary Redpoll (Carduelis h. hornemanni) which has been visiting bird feeders at QUBS Point on an almost daily basis since February 9, 2011. This 14 g songbird has brought birders from as far away as Pennsylvania, Connecticut, Washington DC and New Jersey. To understand why a Hornemann’s Hoary Redpoll should be so popular among birders it’s necessary to know a thing or two about redpoll taxonomy and natural history.

Redpolls are small finches that breed in the high arctic and subarctic and spend the winter mainly south of the tundra throughout North America and Eurasia. There are two species redpolls in North America, both of which breed in low numbers in northern Ontario and winter in southern Ontario in most years. Redpolls are irruptive during the non-breeding season, which means that in some winters there are lots of redpolls and other winters there are few or none in Eastern Ontario. Annual fluctuations in redpoll numbers are usually correlated with fluctuations in the abundance of food sources, typically birch (Betula spp.) seeds. When seed crops are poor in the boreal forest, redpolls wander south in search of other foods including fodder from birdfeeders.

Whenever redpolls are present, Common Redpoll (C. flammea) is the most abundant species, while Hoary Redpolls (C. hornemanni) are far rarer, so they attract quite a lot of attention from birders when they appear. Both of the redpoll species are comprised of two subspecies (in North America). There is the Southern Common Redpoll (C. f. flammea) and the Greater Common Redpoll (C. f. rostrata); and there is the Southern Hoary Redpoll (C. h. exilipes) and Hornemann’s Hoary Redpoll (there are a wide variety of English names applied to each of these subspecies so it pays to know the scientific names too). The Southern Common and Southern Hoary Redpolls breed across the southern Canadian arctic and subarctic. Greater Common and Hornemann’s Hoary Redpolls breed further north, on Baffin Island, Greenland and in the case of Hornemann’s up to Ellesmere Island! Of the four subspecies, Hornemann’s is certainly the rarest in Ontario. It is only reported in some winters, particularly when there are large irruptions of redpolls.

It’s not uncommon to find both species of redpolls in the same flock, and sometimes three or even all four subspecies can be found together. This winter we’ve recorded all four of the redpoll subspecies at QUBS. Southern Common Redpolls are by far the most numerous with flocks sometimes in excess of 100 birds. Greater Common Redpolls and Southern Hoary Redpolls are seen singly or in pairs within these large flocks. The single female Hornemann’s Hoary Redpoll always appears with other redpolls where it can be easily recognized by comparison with other birds. Compared to the others the Hornemann’s Hoary Redpoll has whiter plumage, less streaking on sides, nearly all-white undertail coverts, more robust head and neck, smaller beak and is noticeably larger.
Its rarity, its size and its extreme northern breeding habitat make Hornemann’s Hoary Redpoll an attractive target for birders, hence the many visitors we’ve received at QUBS in the past two weeks. Redpoll identification can be difficult; in fact it is one of the most challenging identification problems birders face. Direct comparisons between individuals can be helpful and it is necessary to clearly see all field marks in order to properly diagnose which species or subspecies a redpoll belongs to. A good summary of redpoll identification by Ron Pittaway can be found at http://www.jeaniron.ca/2007/Redpolls/redpolltext3.htm.

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