Saturday, October 23, 2010

Fall banding: Week #10 in review

Banding took place on five mornings this week, with several marred by the continued invasion of the banding area by deer. We banded 133 new birds of 24 species. The composition was decidedly autumnal: robins, sparrows, and kinglets dominated. An Orange-crowned Warbler and a lingering Blackpoll Warbler were the only warblers banded; Yellow-rumped Warblers remain conspicuously scarce.

There are many hundreds of Common Grackles and Red-winged Blackbirds in the area these days. Thousands are feasting on the sunflowers planted by Ford Motor Co. Large flocks, with a few Rusty Blackbirds mixed in, find their way to campus every day. They favor raiding the oak trees that are near, but not in, the banding area, so we usually don't catch too many. In fact, this was the first red-wing of the season:

This is an adult male. By next summer, the brown edging on his feathers will wear away, and he will have the jet black look we are more familiar with.

We have only banded about two dozen Brown Creepers since 1992. It is always a treat to get one of these delicate and sort of odd little birds.

We also don't band many White-breasted Nuthatches. In the fall, I'm twice as likely to catch a Red-breasted Nuthatch, even though we have few conifers and they tend to just pass through, than I am a White-breasted, although they are common residents.

Note the very gray cap contrasting with the darker nape, indicating this is a female.

We are still gathering good numbers of seed samples to determine dietary preferences of birds on fall migration. The composition is changing, with crabapples now showing up in samples as these fruits ripen. Earlier this season, I showed you that seeds are not the only thing we find that birds have consumed. This robin dropping contained a surprise. The dark seed is from Common Buckthorn, the light ones from Amur Honeysuckle. The other object is a jewelry clasp.

By this time of year, we usually spend quite a few mornings loitering around waiting for frost on the nets to melt, provided we have even been able to open them (they are rolled up when not in use, and can freeze shut). We had our first two frosty mornings of the season this week. It's hard to catch birds when the nets look like bed sheets.

The forecast is once again for mild weather, though, so we don't anticipate frost for the beginning of the week, although wind might be a problem. Somewhere, I have a photo of nets full of leaves....

Saturday, October 16, 2010

Fall banding: Week #9 in review

This week had great days, and very boring days, kind of strange for this time of year. Over five mornings we banded 103 new birds and had 22 recaps -- a higher proportion of recaptures than recent weeks, indicating birds are sticking around a bit. We've recaptured 5 kinglets (both species); typically we only recapture two a season of these wandering sprites.

Warblers are lingering, with four species banded this week: Black-throated Blue (below, putting us at nearly double our usual fall average), Nashville, Orange-crowned, and Common Yellowthroat.
We've only banded a few Yellow-rumped Warblers so far, and really haven't seen a large influx of them yet.

As is typical of this time of year, it's Sparrowpalooza time. Six species of sparrows were banded this week.Field Sparrow.

Fox Sparrow.

White-crowned Sparrow (with young, hatching-year birds like this dominating).

And Song, White-throated, and Dark-eyed Junco.

Hermit Thrushes seem to be around in typical numbers after last year's diminished season total of 27. We've had 30 so far. Due to improved collection techniques, we have obtained seed samples from about 57% of the Catharus thrushes we've handled this year, up from the previous three-year average of around 44%. Already our overall collection of seed samples has revealed different proportions of seed species in the droppings of bird compared to the past few years. Fruit crops can vary from year to year based on weather, pollinator availability, and perhaps "built-in" cycles. Our long-term study of these dynamics will help us understand which species of fruits are consistently important, and which are only used in the absence of others -- important data for habitat management.

And finally, we are preparing for our annual fundraising campaign. The University does not provide any funding for RRBO. It all comes from outside sources, with a large proportion coming from individual donors. If you aren't on our mailing list, please consider adding your name. You can also cut to the chase, and donate today!

Sunday, October 10, 2010

“Yellow” Palm Warblers

Palm Warblers (Dendroica palmarum) have two races — “Western” Palm Warbler (Dendroica palmarum palmarum) and “Eastern” or “Yellow” Palm Warbler (Dendroica palmarum hypochrysea).  The western race is found in Michigan, and The Birds of Michigan reports that the eastern race (which breeds from Quebec to northern New England) is “at best casual” in the state and gives one documented record, a bird banded in Kalamazoo in 1990.  The Rouge River Bird Observatory banded an eastern Palm Warbler on 1 Nov 2003 (which also represents a late date for Palm Warbler at this site).

This bird was a hatching-year (or juvenile) bird, based on the incomplete ossification of the skull.  It had no chestnut on the crown, and a fairly short wing, suggesting that it might be a young female.

Eastern Palm Warblers are very yellow in all plumages, while western birds are duller. The supercilium (eyebrow) is yellow, while in western birds the face is much browner, and the supercilium is buff-colored.  The entire breast and belly are yellow in eastern birds, with no contrast between the belly and the undertail coverts. Western Palm Warblers have buff bellies (which can be washed with yellow in fresh plumage) which always contrast with the brighter yellow undertail coverts.

Craves, J. A.  2003.  “Yellow” Palm Warbler (Dendroica palmarum hypochrysea) banded in Wayne Co. Michigan Birds and Natural History 10:99-100.

More “Yellow” Palm Warblers

Since this record, four more “Yellow” Palm Warblers have been recorded in Dearborn.
Two were sight records. One was along the channelized portion of the Rouge River on 5 Apr 2006, seen by Cathy Carroll; this is the earliest recorded spring arrival date for Palm Warbler in the city. The second was seen on a regular spring bird survey on campus,  29 Apr 2009, by Julie Craves.

Two more “Yellow” Palm Warblers have also been banded. The bird on the right was banded on 6 May 2008.  Note the bright yellow supercilium and the chestnut coloration of the breast streaks, and once again the uniform yellow coloration of the underparts. The shorter wing measurement of this bird could mean it was a female, although the crown patch was quite extensive which is more typical of a male. Thus, to be conservative, we left the bird sex as unknown.

On 9 October 2010, another “Yellow” Palm Warbler was banded (below). This was a hatching-year bird, as determined by the incomplete skull ossification. It had many chestnut-colored feathers in the crown over a broad area, although they were concealed, and a long wing measurement. This indicates the bird was a male. It was as bright or brighter than the 2003 bird, with some of the chest steaks also having a chestnut coloration.

For comparison, here is a typical fall “Western” Palm Warbler, of the form that is typically found migrating through Michigan:

Saturday, October 9, 2010

Fall banding: Week #8 in review

We banded all 7 days of week #8 (3-9 Oct), but several days were shortened by having to replace nets destroyed by deer. The deer herd on campus has gotten so large that we had to resort to surrounding the entire banding area in deer fencing several years ago. Due to budgetary constraints, we used relatively inexpensive plastic fencing which requires continual maintenance. Six got in earlier this week when a tree fell on the fence, causing considerable damage over several days.

Nonetheless, we banded 179 new birds of 30 species. Our best day was 5 Oct, when we handled a total of 63 birds. We breached our season high record for Blue Jays, which was set during our first season in 1992 with 19 birds. We're at 22 for the season now. Many banding stations east of us are having a banner year for kinglets, and it looks like we could be on track to break our own records as well, especially with Golden-crowned Kinglets.

This week was also the first strong showing of Hermit Thrushes. The most fecal samples I have obtained over the last three years for our dietary study was 41 from Swainson's, Gray-cheeked, and Hermit Thrushes combined. We're over that total already, with the bulk of Hermit Thrushes yet to come.

Speaking of thrushes, I recaptured a Gray-cheeked Thrush on 7 Oct that I originally banded on 1 Oct. It had a decent amount of fat upon first capture, and weighed 35.2 grams. When I recaptured it, it had piled on the fat and weighed 45.1 grams, an increase of 28% of its original mass in just six days. This is noteworthy, but not unusual for this species here. Gray-cheeked Over 25% of the Gray-cheeked Thrushes we've recaptured gained greater than 20% of their original mass, and about 10% of them gained more than 30%. This is especially interesting given that this species winters in northern South America. They have a long way to go, and it seems unusual for a bird to gain so much weight so early in their migration.

There were two highlight birds this week. First up was a young male Yellow-bellied Sapsucker banded on 4 Oct. This is only the fourth we've banded here since 1992. They are not uncommon here, but usually hang around above net-level.

The other bird was banded today (10 Oct) -- a Palm Warbler of the eastern or "Yellow" race, which nests east of Ottawa and usually migrates east of the Appalachians. We banded one in 2003 (photos and more info on the RRBO web site) and 2008 and have two spring sight records.

Yellow Palm Warblers, in addition to being slightly larger than the western form that typically migrates through Michigan, have very yellow underparts, with little contrast among the throat, belly, and undertails coverts. Overall they are more washed with yellow, including a yellow supercilium.

Western Palm Warblers, especially in fall, are pretty dull. Here is one from earlier this month:

Even in spring plumage, western birds have brownish chest -- you can see how it contrasts with the throat and undertail coverts in this spring bird in Florida (photo by Len Blumin):

Today's bird was a young (hatch-year) bird that was as bright or brighter than the 2003 bird, which had a short wing measurement and no chestnut color in the crown, indicating it may have been a female. Today's bird had many concealed chestnut crown feathers over a large area and a longer wing, making it a male.

I've updated the Palm Warbler page at the RRBO web site with some new photos later in the week. We average about nine Palm Warblers a fall season, and we are a few bird over that total so far this year -- maybe we'll have a few more individuals to show the range of western Palm Warbler plumages in fall.

Sunday, October 3, 2010

Fall banding: Weeks 6 & 7 in review

The last two weeks were characterized by some odd weather. Week #6 (19-25 Sep) featured a return to summer, with very warm weather and substantial south winds, not so good for migration. Last week (26 Sep-2 Oct) began with more of the same, and ended up with an ubrupt change to more autumn-like conditions, although wind and rain were involved. Thus, five full and two partial banding days were lost to weather.

For the period, we had 189 birds of 35 species. The wide diversity of warblers typical of mid-September began to give way to the birds of fall: White-throated Sparrows, Hermit Thrushes, more American Robins. Blue Jays are migrating right now, and we've been catching more of them. It's pretty easy to tell a young blue jay from an adult. As in quite a few species, there is a difference in the shape of the outer tail feathers. In young birds, the first set of tail feathers is usually more pointed:

In older birds, these feathers tend to be blunter:

In theory, this can help you age the bird. In practice, if a young bird loses its tail feathers, they will grow back with the adult form. So if a jay has adult-shaped feathers, you need to have at another characteristic to verify the age. The primary coverts (the feathers that cover the bases of the outer flight feathers) and adjacent alula of young jays are dullish blue-gray or brownish-blue:

In adults, they are brighter blue, and usually barred:

These photos aren't the greatest to illustrate this -- in a lot of jays the differences are pretty obvious, while these individuals were not the best examples.

We had nine recaptures of birds we previously banded. The highlight was the Indigo Bunting that turned out to be oldest Indigo Bunting ever reported recaptured by a bander in North America. There were four birds from last year (Downy Woodpecker, Black-capped Chickadee, American Robin, Song Sparrow), and three from 2008 (Hairy Woodpecker, 2 Gray Catbirds), and a Northern Cardinal from 2005.

On Sunday, September 26 we hosted an informal bird program for a Detroit Audubon Society field trip. A nice group showed up, and they got to see a variety of species. Most of the warblers were banded after the group left, unfortunately! Birds banded were: Blue Jay, Black-capped Chickadee, Philadelphia Vireo, Red-eyed Vireo, Swainson’s Thrush, American Robin, Gray Catbird, Nashville Warbler (below), Magnolia Warbler, Cape May Warbler, Blackpoll Warbler, Wilson’s Warbler, Common Yellowthroat, Lincoln’s Sparrow, White-throated Sparrow, Indigo Bunting, Northern Cardinal, and American Goldfinch.

Friday, October 1, 2010

Super senior P. cyanea

One of the most interesting birds banded this season was not an unusual species, but an unusually old bird. Most small songbirds do not make it through their first year -- they have about an 80% mortality rate. If they make it through their youth, many only live 2 or 3 years. Resident birds tend to live longer than migrant birds, and the farther a bird must migrate each year, the more hazards it faces, and the shorter the typical lifespan.

Indigo Buntings nest over much of the eastern U.S., and winter in the West Indies and Central America, and are therefore considered long-distance migrants. This male Indigo Bunting was first banded as a "second year" bird on 23 August 2003. Thus, it was hatched in the summer of 2002. We recaptured it in May 2006 and May 2007 when it was in breeding condition. This many round trips is pretty remarkable itself.

We caught him again this past week, on 29 Sept. Based on the way age calculations of recaptured birds are made, this makes this bird 8 years and 3 months old -- which happens to be a longevity record for this species in North America, according to the longevity records kept by the Bird Banding Lab. The previous record was an 8-year-old bunting in West Virginia -- a record that stood for the last 48 years.

You can take a look at some of the other birds we have recaptured years after their original banding on this page at the RRBO site. Note that on that page, the "age" indicated is the period that has elapsed between captures, not a calculated age.