Black-capped vs Carolina Chickadees

I am glad that we Minnesotans have Iowa, Wisconsin and northern Illinois separating us from Carolina Chickadees, the bird in the upper photo. Telling the two species is very difficult. Several subtle field marks exist. The first is the sharp demarkation between the black throat and the white breast in the Carolina and the Black-cap's more ragged throat line. This difference is obvious when you compare the Carolina Chickadee above (from northern Florida) and the Black-capped Chickadee in the next photo (taken in New York). Be warned that this mark is of less use in Carolinas with warn fall plumage.

The Black-capped Chickadee's wing coverts and primary edges tend to be white, whereas these feathers in Carolina Chickadees tend to be uniformly gray. You can see these pale edges on the Black-capped Chickadee that I published in a recent post from the Carleton College Arboretum. Again worn Black-capped plumages will give the unwary trouble. Two more field marks, less reliable than others, are that Black-capped Chickadees tend to have rustier flanks and whiter napes. These marks are (sort of) visible in the first two photographs. Black-capped Chickadees tend to be larger than Carolinas, but the size overlaps.

Finally, the two chickadees have different calls. The trouble is that, in the areas of overlap across the central United States, the two species learn each other's songs. To further confound identification, these chickadees also hybridize, blending characteristics. I think convincing the Minnesota rare bird committee that you have seen a Carolina Chickadee in our state would be a difficult task.

Review of Dragonflies and Damselflies of the East

I am excited whenever a new book is delivered to my door. But I am particularly thrilled with the just-published Dragonflies and Damselflies of the East by Dennis Paulson. Finally we have a guide to the Minnesota Odonata. Last September, I reviewed this volume's western counterpart. I lamented it only included species east to the Dakotas. With both volumes, we now have a chance to identify any Odonate in Minnesota, the United States, and Canada!

An astounding 336 species are covered in this guide, and all are accompanied by at least one stunning color photograph. One drawback to photographs (instead of drawings) is that they show their subjects at different angles. Photographs are also liable to distortion of color due to shade, sun, and camera exposure. Geographically variable species are hard to illustrate with single photographs or single drawings. These guides lack the user-friendly field mark arrows found in other nature guides. (I understand that Peterson copy-righted his arrows.) Many of these creatures are hard to identify and some require microscopic examination.

Species accounts, along with identification tips, cover a description of each species. Also included, along with small but fascinating range maps, are dragonfly natural history, habitat, flight seasons, and short comments, including taxonomic problems or other tidbits. As in the Western guide, the species accounts are preceded by a wonderfully illustrated account of Odonates in general, their life histories, ecology, behavior, flight seasons and reproduction--a must read for anyone wishing to learn about dragon and damselflies. At under $20.00 from Amazaon.com (list is $29.95), this guide is truly a bargain that all naturalists will enjoy. I am excited for next season's Odonata and for future road-trips across the country!

The photo below is of a female White-faced Meadowhawk. This abundant Odonate will sometimes perch on any tall vantage point, as Erika and I know for a fact.

Great Horned Owl

As Erika and I walked through the pine forest in the Carleton College Arboretum, I commented, "I wonder why we don't see owls in this forest. It seems perfect." No sooner were the words out of my mouth, when spied an owl-like lump high in one of the trees. A Great Horned Owl sat there, facing away from us. Nevertheless, it did not take long for it to be alert to our presence. The owl then did a curious thing. It ran along the branch (see lower photo), presumably to get to a more convenient take-off location. And off it flew.

Great Horned Owls are bad news for resident Barred Owls. According to the Cornell Laboratory of Ornithology, the Great Horned Owl, which prefers large tracts of territory, "is the most serious predatory threat to the Barred Owl. Although they often live in the same areas, the Barred Owl will avoid parts of its territory occupied by a Great Horned Owl." But it is a rough world out there, since Barred Owls, in turn, often prey on Northern Saw-whet Owls.

Bathing Chickadees

On Tuesday 10 January 2012, Erika and I strolled through the Carleton College Arboretum in Dakota County,  Temperatures were record-breaking, in the low-50 degrees F. We have suffered through a snowless winter, and the forest floor was exposed. The trails were basically dry, except for a bit of ice under a shady pine forest. The ice was melting, with pools of water in depressions and along side of the ice.

We found a flock of six Black-capped Chickadees bathing in the water. The birds flew back and forth between the pools and bushes along side the trail. Open water must be a rare, January delight for these winter residents. As we returned from our outing, we came upon the same chickadee flock, still hard at work at their bath. Now the chickadees were joined by a few juncos, a Red-breasted Nuthatch, several White-breasted Nuthatches, and even a Brown Creeper.

Ring-billed Gull

Erika and I also listed a Ring-billed Gull at Black Dog Lake just south of Minneapolis. A common species, this young bird was easily identified by its relatively small size and by the black band at the end of its tail. Previously I blogged about this species. A quick look at eBird shows that Ring-billed Gulls range across most of the United States during the winter, with Minnesota being near the northward limits. This gull, an opportunistic forager, probably depends on open water and ready winter food sources.

Iceland Gull

Despite the warning from Eckert in A Birder's Guide to Minnesota that "paler Thayer's and darker Icelands appear similar, if not identical," Erika and I identified this gull, on the ice on the Minnesota River near Black Dog Lake, as an Iceland Gull. Keys to identification include the almost completely white underwings and extremely pale head and breast. Other birders have photographed adult Icelands in the same area.

Snell (2002), a gull expert, believes that Thayer's and Icelands are but one highly variable species. He notes that field marks broadly overlap. Not only are birds of extreme plumages found across their breeding range, pale and darker birds also breed freely with each other. Snell concludes, "Based on this, I believe only 1 species should be recognized with all taxa placed under Iceland Gull." Adopting his recommendation would certainly make life easier for us birders!

Franklin's Gull

Yesterday, on our third trip to Black Dog Lake, Erika and I found a much-reported Franklin's Gull. With its black-smudged head and white-spotted primaries, identification is fairy clear. The trouble is that this gull should be wintering in the Pacific Ocean off the coast of western South America (mostly off Peru and northern Chile). A look at eBird demonstrates that December through February records in the United Stated are sparse, limited to coastal areas and scattered through the central states.

This species breeds in prairie marshes in the upper Great Plains. They can be abundant during migration as they follow farm machinery that turns up insects. They feed both in the air and on the ground. Franklin's Gulls often abandon disturbed breeding colonies and are subject to the unpredictability of prairie droughts. Their numbers, therefore, often fluctuate. Recently only 36 breeding locations were counted in Canada and 21 from the United States. Colonies can contain over 10,000 pairs (Burger and Gochfield 2009).

Bald vs Golden Eagle

Erika and I also photographed a Bald Eagle at Black Dog Lake (see last post). First year birds like this one can be confused with Golden Eagles. Both species can show a black band at the end of the tail, but the base of the Golden Eagle is more uniformly white, whereas the tail is usually duskier in the Bald. The transititon from whitish to dark on a Golden Eagle is usually much more cleanly abrupt. Note the field marks in the Golden Eagle below--distinct tail band, white tail base, and white wing patches. Note that Bald Eagles have some white in the wings and the Golden Eagle's nape patch can be hard to see. In Minnesota, Bald Eagles far outnumber Golden Eagles.

Herring vs. Thayer's Gull

Erika and I photographed the Herring Gull above last Wednesday near Black Dog Lake south of Minneapolis. Gulls are hard to identify. First you are dealing with about three dozen species that are basically white, gray, and black. For the first three or four years of a gull's life, individuals often show distinct plumages. Gulls are notorious wanderers, so birders are often confronted with out-of-range species. If this situation was not confusing enough, gull species exhibit numerous races. Not only do these races interbreed, the species themselves occasionally hybridize. 

This adult Herring Gull is basically white below and gray above. The yellow bill has a red spot and the wings are liberally black-tipped. Some winter adults, as well as Herring Gulls from the North Pacific ("Vega Gulls"), show more neck streaking. Herring Gulls are found in northeastern Minnesota in the summer and across the state in other seasons. When I studied the half-dozen South Dakota banding records, I was surprised that all the state recoveries were of birds banded in New Brunswick, Canada. I do not know if these Herring Gulls wandered directly across the continent, or first wintered in more southerly areas.

Compare my Herring Gull to a bird I assume is a Thayer's Gull from Prescott, Wisconsin, several winters ago. This bird clearly has a darker neck, although this field mark is variable in Herring Gulls. The under side of the wing appears only slightly black-tipped. The eye color appears to be different--pale in the Herring, dark in the Thayer's--another variable trait in some Herring Gulls. Iceland Gulls are also very similar and, in fact, sometimes indistinguishable from Thayer's Gulls. Usually Icelands tend to be paler. Thayer's Gulls breed in the High Arcrtic. They are being listed more frequently in recent years, as birders become more proficient at gull identification, but many are misidentified. If you are confused by this blog post, I urge you to read Eckert's more detailed account in A Birder's Guide to Minnesota.

eBird Birding

Not all arduous jobs are unpleasant. I have been transcribing my life list into eBird. I have listed over 2,000 species in 51 years of birding. One problem is that, during this time, our understanding of avian taxonomy has been revolutionized. Consider these Masked Boobies Erika and I found in the Galapagos Islands on 30 April 1976. Since then, mitochondrial DNA studies indicate these Galapagos seabirds are a distinct species, the Nazca Booby. (The two species have different bill and feet colors and as well as behavioral differences.) To my delight, last February I listed Masked Boobies in Florida's Dry Tortugas. At the time I was disappointed the Florida birds were not new for my list. What a lovely present from eBird--a new bird--and a great example of why birders should keep complete lists--not just the new ones in life lists or year lists--of the birds they encounter.

Nazca Boobies practice obligate siblicide. They lay two eggs, but the elder chick always pushes the younger sibling out of the nest. The parents do not intervene. Only if the first egg fails to hatch, does the younger sibling survive. This behavior has been linked to high levels of testosterone and androgens in the hatchlings (Wikipedia).