Monday, September 30, 2013

Why are Yellow-rumped Warbler so common to see in fall migration?

Joan (in Boston):

Here's why you see Yellow-Rumped Warbler in many different habitats and, especially, en masse during a prolonged spring and autumn migration (in the Midwest and East):

1. Among the four subspecies in the Yellow-Rumped Warbler (YRWA) species, one is the Audubon subspecies (including the male Audubon YRWA seen in the above photo). 

2. YRWA exploit multiple feeding niches within the profile of the forest. That is, you are as apt to see them in the interior branches near the main trunk as you are to notice them near the ground. As a “hover and gleaner” feeder (like many Dendroica genus wood-warbler members of which the YRWA is enrolled), you can expect to see YRWA in a forest profile, but they also might be at the seashore (finding invertebrates near the surf) or, even, on grassy lawns (where insects may provide food resources). 

3. In turn, given YRWA is able to exploit multiple environments and feed on diverse food resources – from insects, to fruit (such as poison oak and poison ivy berries, in addition to privet and wax myrtle berries – the species is well-adapted to sustaining its populations in times of food scarcity. That is to say, the YRWA has a diversified portfolio – a perfect tactic to ensure that the boom and bust of food resources does not impact the species’ numbers.

4. The hydrochloric acid content within YRWA individuals appears to be more potent than the digesting apparatus contained within most other wood-warblers. In fact, the wax myrtle berries that help YRWA survive harsh conditions in winter along the mid-Atlantic are not digestible by most birds, including the 51 other wood-warbler family members typically found annually in North America north of Mexico. Given the abundance of wax myrtle, YRWA are able to survive into the deep fall (and sometimes throughout the winter) in states that often encounter harsh winter conditions: WI, MI, OH and, in the East, MD, VI, NY (and in some New England states during some winters). 

Seeing YRWA in November and December, thus, is not uncommon in the states mentioned immediately above. Increasingly warmer winter seasons, too, provide succor to YRWA that do not need to vacate northern latitudes as is the custom in the vast majority of other songbirds.

(Note: This article originally appeared at this blog in a similar form, but I receive periodic queries about this question as answered above, so I decided to post this article again, given Yellow-rumped is annually common throughout northern latitudes in late September/October.)

Thursday, September 26, 2013

Sound Answer?: Can you identify the warbler singing in the background?....

.....and if you go to:

Listen to the 2nd version of the Nuttall's Woodpecker from the top of the page*.

Which warbler is singing in between call notes of the woodpecker?

(* = The 1:01 recording is from the work of Thomas C. Graves.)

Hint: It's an early arrival in central and northern California, with migrants arriving
as early as the first week of February some years.

If you seek the answer, please email me and I'll reveal it:
(The subject of the answer is shown below.)

Meanwhile, I have a San Francisco bird tour soon, so I am getting ready to leave...and, hence, will do the same here. Enjoy. DE.

Sunday, September 15, 2013

Warbler Guy, now that the leaves are starting to fall in my northern locale, I found a couple of warbler nests. Hence, is there a newer bird nest field guide than the great, yet limited Hal Harrison East & West Coast bird nest books?A Guide to the Nests, Eggs, and Nestlings of N. American Birds. Paul J. Baicich & Colin J.O. Harrison, Academic Press, 1997, 2nd edition

Sherry, you are in luck, given the following recent 2011 publication Nests: Fifty Nests and the Birds That Built Them (Chronicle Books). In it, Sharon Beals features amazing photos of USA bird species, including the one shown here: Golden-winged Warbler (which, by the way, is a Watch List* species according to the National Audubon Society, meaning it's numbers appear to be decreasing in portions of its breeding range, per census figures).

(* = See

So, start your Nest Search Engines, people (and Sherry), as this species would truly be a jewel to find.....and I am lucky to note that I saw one migrating Golden-winged recently in Wisconsin
during a birding trip to find warblers and other avian migrants.

Meanwhile, the Harrison guides round out my nest library of, along with A Guide to the Nests, Eggs, and Nestlings of N. American Birds (Paul J. Baicich & Colin J.O. Harrison, Academic Press, 1997, 2nd edition)