"Gambel's" White-crowned Sparrows

A western form White-crowned Sparrow (Zonotrichia leucophrys) was banded by the Rouge River Bird Observatory on 20 October 2006, described below and compared with typical eastern and “intergrade” forms. There is a very nice article on identifying subspecies, with range maps, in a 1995 issue of Birding (27:182-200). Two other web pages, Oiseaux Birds and David Sibley’s blog also have a nice set of comparative photos of some of the variations.

Adult White-crowned Sparrows of all subspecies have black and white head stripes, while juvenile birds have brown and tan head stripes. Here are some examples of juvenile White-crowned Sparrows banded at RRBO, concluding with the western “Gambels” type banded in 2006.

Above is a  typical eastern hatching-year White-crowned Sparrow (Z. l. leucophrys).  Characteristics include a deep-based, pinkish bill with a dark tip, a medium-brown crown stripe, and a dark line through the eye that connects to the crown stripe in front of the eye.

This White-crowned Sparrow, banded on 16 Oct 2006, shows traits of an intergrade between the eastern form and the western “Gambel’s” White-crowned Sparrow form. Bill shape and color and crown color are similar to the eastern form.  The lack of dark feathering between the eye and crown is more like the western forms.

This White-crowned Sparrow banded on 20 Oct 2006 is most like the western “Gambel’s” form (Z. l. gambelii).  It not only lacks dark feathering between the eye and crown, but has a thinner, orange bill which is yellowish at the tip (described as looking like “candy corn”), and a more rufous crown stripe coloring.

This adult White-crowned Sparrow banded on 22 Oct 2012 is also a good candidate for the western “Gambel’s” form. It obviously lacks dark feathering between the eye and crown, the bill shape is farily narrow, but the bill color is a little ambiguous

Banding update

We are well on our way to banding the fewest birds in any fall season in 20 years! The fewest new birds we have banded prior to this year was 739 in 1996. Our "slowest" year was actually 2008, when our capture rate (birds banded as a function of the number of nets we used and the number of hours we had them open) was 33.4 birds per 100 net hours. You can see our current numbers in the right sidebar. I'm pretty sure there is not enough time left in the season for this year not to come in dead last in both categories.

While a lack of birds is disappointing (and kind of alarming), these low numbers are providing valuable data.The weather this growing season is mostly responsible, in particular the drought.  In a previous post, I noted the low numbers of young birds we were banding. This has continued to be the case. American Robins in particular have exemplified the kind of season we are having.

The average number of robins we band in fall is 188, with 300 or so not being uncommon. Prior to today, we had banded only 15!! Today we had 17 more, bringing our total to 32, a remarkably low number.

Based on our 1992-2011 fall data, we can expect around 76% of the robins to be hatching-year birds. This year it is only 23%. This is an indication that robins failed to fledge a "typical" number of young. Since many of the robins we are catching now are migrants likely to have nested elsewhere, this suggests that nesting failure was not just a local problem. And indeed, the drought covered a very large part of the continent.

One interesting aspect is that nearly half young birds I have captured recently still had some spotting on their breasts; this is the plumage they have when leaving the nest. Typically, only about 3% of hatching-year birds have spots this late in the season, having already mostly completed their fall molt. Similarly, 61% of the adult robins are still completing their fall molt. In the past, only about 16% were still molting at this time of year. It looks like, then, that many robins nested late this year -- probably after losing an earlier brood.  It's possible that the skewed ratio of young to older birds may even out a bit in the next couple of weeks.

The prolonged and severe drought contributes to low reproductive success by diminishing food supplies, especially for birds like robins that utilize a lot of leaf-litter or soil invertebrates to feed their young. Besides just reducing the number of birds available, the dry weather contributes to our low capture rates by impacting the fruit crop. Our very early spring heat wave also compounded the failure of many types of wild fruit, as I discussed earlier in the season. Fruit is a vital food source for many species of migratory birds, and of course, a main topic of our research.

In short, many of our staple fruiting plants had small crops or did not fruit, or fruited later than usual. I noted that locally, fruit crops were better in areas adjacent to water. Our banding site is not (unlike many banding stations, which are located in some sort of coastal situation). So this year provided interesting insight into the impacts of growing season weather.

In a future post, I'll provide an update on the 2012 fruit crop and what we found birds were eating.

Silent Spring after 50 years

Have we learned our lesson?

Fifty years ago this month the important book Silent Spring by Rachel Carson was published. This book warned about the lethal and persistent effects of the pesticide DDT. This book, while in some ways outdated, remains a classic not only for its role in inspiring environmental stewardship, but also because although DDT has been banned in the United States, as a society we still enthusiastically embrace a whole suite of chemicals that end up in our air, water, and soil (and ultimately in animals and ourselves). And we still tend to trust that they are perfectly safe.

In fact, testing of pesticides and other chemicals is focused specifically on active ingredients used in certain amounts and circumstances. Many people use chemicals in ways not intended by the manufacturers, in amounts beyond recommended volumes, in combination with other chemicals, and when none are really needed in the first place. Aside from the risks of these types of applications, we further know very little about the components of this toxic soup interact with each other and the environment.

An excellent example is the American obsession with cosmetic lawn and garden chemicals. I don't want to get too soap-boxy here, but I can tell you two things. First, you can have a nice lawn (if you must) and garden without the use of any chemicals. I've done this my whole life. Second, one of the best things you can do for birds (your pets, the ecosystem, and yourself) in your area is to quit using all chemicals in your yard, because they do harm birds.

I see the effects of "safe" lawn chemicals every year on common birds. I have held emaciated robins in my hands as they had seizures and died, and looked up from their lifeless bodies to rest my gaze upon those little signs indicating an expanse of grass was sprayed with some concoction. Without direct toxicology tests, I can't honestly say lawn chemical exposure was the direct cause of these deaths. I do know that robins can't read to keep off the grass, that their symptoms are typical of exposure, and it is far too common an occurrence to not at least suspect that some combination of chemical exposure is to blame.

On this anniversary of the publication of Silent Spring, I encourage you to read or re-read this book and related material. We are in an age where enough data is available for us to be truly informed and where our actions can make a real difference. Unfortunately, we are also at a point where we are distrustful of science, and often bombarded with conflicting messages from special interest groups. I don't have a horse in this race, except my love for the natural world. Here are my recommendations:

An excellent overview of the context and impact of Silent Spring can be found at the Pop History Dig website: Power in the Pen: Silent Spring 1962. The New York Times Magazine also recently published How Silent Spring ignited the environmental movement.

The book itself, Silent Spring (Kindle edition here), as well as a new biography of Rachel Carson, On a Farther Shore: The Life and Legacy of Rachel Carson (Kindle here).

I also strongly recommend Our Stolen Future, which further explores synthetic chemicals in the environment.

There are many excellent sites on thee continued risk of chemicals many of us continue to use regularly. The non-profit Environmental and Human Health published a report very worth reading: Risks from Lawn Care Pesticides. The organization Beyond Pesticides has extensive information about pesticide issues, risks, and alternatives.

MIA: young birds

In our last update, I mentioned that I thought the hot, dry summer might have resulted in low productivity -- fewer young birds fledged. Fall banding is an excellent way to assess productivity, as the ratio of young to adult birds is easy to tally. Here at RRBO, about 81% of the birds we band in fall are young-of-the-year, known to banders as "hatch-year" birds. This is fairly typical, although coastal banding stations may see 90% or higher, since young songbirds often follow slightly different migration routes than adults, and seem to favor coastal routes.

So far this fall, the number of adult birds we are banding has been unusually high. Sometimes we see this in individual species, but it seems like it is across the board so far. I took a look at the first month of fall banding for all years prior to this year combined, and noted that 86% of the birds banded were hatch-year birds. Since we begin banding in August, we usually start out banding a lot of the recently-fledged resident birds, especially catbirds, so the slightly higher percentage compared to the overall fall average is expected. This year so far, only 68% of the birds have been hatch-year.

We will have to see how this plays out over the season. I am especially concerned at the overall low numbers of American Robins and Gray Catbirds, especially young birds. I will address these in a future post.

Let's look at a more cheerful graph -- the composition of warbler species banded so far this fall.

The "other" category are three species for which only single birds have been banded: Black-and-White, Cape May, and Palm Warbler.

Since it's so early in the season, it's hard to say whether or not some of these species will be banded in larger numbers than usual. Nashville Warblers are one our most frequently-banded species; they have a long migration period so this graph is not very revealing. My gut based on the last 20 years is that redstarts may end up being more numerous this year than usual. Right now they comprise 24% of the warbler species banded. The overall fall average is 12%.

It looks like the summer-like weather is gone for the next week, and a dramatic shift in the jet stream over the coming days is likely to bring in lots of birds. Stay tuned.

August banding

Fall banding 2012 started on August 17. As I suspected, things have been slow. The very hot, dry summer seems to have resulted in low reproductive productivity for our most common local breeding bird species, such as American Robins. It's just difficult for them to find ground-dwelling invertebrates to feed their young when it is so dry.

Rather than just summarize numbers this fall banding season, I'd like to focus more on one of our current research projects: the fall diet of birds. As regular followers know, RRBO's research focus is on the fall stopover ecology of migrant birds, in particular what kinds of fruit birds are eating in this urban forest patch. We do this by collecting seeds passed by the birds that we band when they poop in the bags we transport them in. This is the 6th year we have collected samples from Catharus thrushes (Swainson's, Gray-cheeked, and Hermit), and the 4th year we have done expanded sampling on all bird species.

Through 2011, we have collected samples from over 1,000 birds of 17 species. Of the nearly 6,400 individual seeds in these samples, only nine have gone unidentified (I'll describe in detail in a future post how we identify all the seeds). Twenty plant taxa are represented in the samples, and most seeds have been identified to species. Thus, we have a great picture of which species of fruit are being eaten by birds.

Pokeweed fruit.

In August, we collected samples from 18 birds. Pokeweed was the most common seed, showing up in 11 samples. We had our first ever sample of poison ivy from a catbird. Usually, this is consumed by woodpeckers or Yellow-rumped Warblers, and nearly always in October. Like quite a few plant species, poison ivy seems to have flowered (and thus set fruit) earlier this season. Other plants may have budded or flowered early (given the long stretch of hot weather in March), then failed to fruit either due to frost in April, or because of the long dry period in summer. We have virtually no crop of wild grapes or relatives such as woodbine/Virginia Creeper. A number of other shrubs that are staples in the diets of fall birds here are ripening late; some portion of shrubs did not set fruit at all.

Poison ivy flowers

Our data for this hot, dry growing season should be an interesting contrast to last year's exceptionally wet summer and add substantially to our picture of what birds eat during fall in an urban natural area.