Fall 2011 banding: week 2

Another very quiet week, with not many migrants around. A higher percentage of the young resident birds that I'm banding have not yet started or are just beginning their post-juvenile molt than I usually see this time of year. This is the replacement of their juvenile plumage into their first winter adult plumage. It's usually in full swing right now. Same with the molt of adults, who typically molt all of their feathers after they are done nesting. The adults I've banded have just started this process.

The extent of this molt this year tells me that these species -- cardinals, catbirds, robins, and Song Sparrows mostly -- were a little later in fledging than usual. It could be that the big flood in May caused some birds to lose their first nest, and pushed breeding back a couple weeks. Or, good conditions this summer (warm, good amount of rainfall, lots of bugs) could mean some species attempted a third nesting.

I have heard and seen adult birds still tending their newly-fledged young. Here is a brand-new youngster I captured this week. Can you guess the species?

While it seems a little lost and forlorn, I found one of the parents in a nearby net. Although both sexes of this species look alike, they can sometimes be distinguished in the hand. The incubating parent (in most songbirds, just the female) develops a bare area on her belly called a brood patch. The area loses feathering and becomes vascularized in order to facilitate the transfer of heat from her body to the eggs and chicks. I was able to tell that this was the female parent of the chick above.

It's a Chipping Sparrow, a common nester here on campus.

Another frequent nester is the Baltimore Oriole. Because they migrate so early in the season, I sometimes don't catch any in the fall. I had three in one net this week, including this adult male. Orioles are pretty sassy. This one seemed astonished, and a little indignant.

Over the weekend, we had some north winds which brought in some migrants that were observed on our survey on Sunday. This week may bring a small uptick in captures if the migrants stick around, but the forecast is for more southerly winds and hot temperatures toward the end of the week. That could slow things down, but we'll see!

Fall banding 2011 begins

RRBO began the 2011 fall banding season on 12 August. The first week was a "soft" opening, when we put up only a portion of the nets each day, make adjustments, and handle all the young fledglings in the area with some extra TLC. We were also taking some extra time to prepare for a special project, which I'll write about in a future post.

Not too many migrants were present. We caught a Yellow-bellied Flycatcher on 15 August, which was an early date for a fall migrant in Dearborn. A Chestnut-sided Warbler captured on 17 August was the only other passage migrant netted this period. I like the inquisitive look it has.


What we did have was a lot of mosquitoes. This is the worst year for mosquitoes I can remember. In fact, so many come inside with me that they are as bad inside the banding room as many typical years outside.

The coolest bird we caught was not uncommon -- a male Northern Cardinal. But it was a bird we had banded on 19 April 2001 as a second-year bird. Thus, he is now over 11 years old, the oldest cardinal we have recaptured and the second oldest bird we have ever recaptured. While 11 years falls short of the record listed at the Bird Banding Lab web site of over 15 years, it was still good to see him. Over the years he has been recaptured 21 times, but the last time was in 2009.

This is our fifth year of studying the diets of fall migrant birds on campus. We're off to a good start with our sampling of seeds in the poop of various birds. These are all from robins and catbirds.

Just about every species of fruit that is currently ripe has showed up in the samples: grape, pokeweed, glossy buckthorn, dogwood, cherry, and nightshade.

Speaking of robins, three of the six robins we've caught so far have weighed less than 60 grams and have been fairly emaciated. By comparison, only six robins out of over 3500 previously banded here have weighed less than 60 grams, and the average weight for robins is about 78 grams. Generally, I only see birds like this when they are on death's door, and often after they have been exposed to lawn chemicals. I don't have an explanation for the lean condition of these birds, but we'll be monitoring future captures carefully.

Finally, it looks like it may be a very good year, the first in some time, for chickadees. Over the decade between 1992-2002, the resident chickadee population on campus was on the decline. Last fall, there was a large movement of chickadees in eastern North America. It was notable here, and I wrote about it after our last Winter Bird Population Survey season. Clearly, many chickadees chose to stay and nest here, as they were evident on our spring survey as well. We've already banded nine, which is our average over the past nine years. Our high was 52 in 2002. As you might imagine, they are quite the little fussbudgets. I'm happy that their numbers are rebounding, but not so sure I want to band a record number of them.

A Black-capped Chickadee was the first bird banded by RRBO during our inaugural fall season in August 1992. That's right -- this is RRBO's 20th fall banding season. Stay tuned for anniversary-year news.

Dearborn Goldfinch in Ontario

RRBO recently received notice that one of the 2500+ American Goldfinches banded here on campus was recovered elsewhere. Only about 1% of small songbirds banded are found away from the place they were banded, so a report of this kind is always interesting. Usually, birds are not found far away, and usually they are dead. This report indicated that the goldfinch in question, a hatching-year male we banded here on 19 October 2010, was captured and released by another bander north of Guelph, Ontario (about 175 miles from Dearborn, as the goldfinch flies) on 10 May 2011.This has happened only a few times for RRBO: a Yellow-rumped Warbler caught in Tallahassee, FL, a White-throated Sparrow on Ontario's Bruce Peninsula, and a Northern Waterthrush in Wisconsin. What made this American Goldfinch capture even more special was that it was captured by Antonio Salvadori.

Toni has been banding for nearly as long as I have been alive, founded the Guelph Banders Group, and bands at three locations. One is at his home in Guelph; another a property in Ermosa, just outside of Guelph; and at Colwyn Farm, northeast of Guelph near the town of Fergus. But here's the kicker. In 2008, Toni captured and released a Blue Jay banded in the east Dearborn yard of RRBO's Julie Craves and Darrin O'Brien. He caught the jay at his Ermosa, Ontario location. It's hard to imagine the odds of this occurring. I might expect that Black Swamp Bird Observatory would capture some of our birds, or vice versa, given their volume and location on the north shore of Lake Erie about 50 miles nearly due south of RRBO. So far, this hasn't happened...

Spring migration 2011

The spring 2011 survey season took place 1 April through 15 June. On campus, regular surveys were conducted on on 50 of the 70 days, with nearly daily surveys between 20 April and 3 June. The surveys recorded 146 species (another 15 were recorded in Dearborn off-campus). This is greater than the previous ten-year average of 130 species, or the five-year average of 133. The peak day was 10 May with 95 species, of which 25 species were warblers. Typically, our peak day is around 80 species and occurs later in the month (May 16-20 the past three years).

Weather
Spring 2011 was the second wettest spring on record for Detroit, according to the National Weather Service. April was generally cool, with measurable precipitation 18 out of 30 days and a rainfall total 2.5 inches above normal. May featured normal temperatures, and 21 days of precipitation. This included a dramatic soaker on May 25-26 with over 2.5 inches of rain on campus that caused the Rouge River to peak at least five feet above flood stage (upper left in photo is the waterfall at Fair Lane Estate, inundated by the high water). The month ended up being the second wettest May on record.

Highlights
Thirty species of warblers were recorded on campus this spring. This includes all 26 regularly-occurring species (at least 8 of the last 10 years), as well as the less-common species Pine Warbler (26 Apr), Prothonotary Warbler (9 to 11 May), Kentucky Warbler (10 May), and Hooded Warbler (18 and 22 May).

In general, migration was excellent this year, which has not been the case for the past five years or so. In addition to great diversity, numbers were also better. Early season migrants were especially abundant. The two eBird graphs below show two of these species, Yellow-rumped Warbler and Palm Warbler for the last five spring migrations. Lines represent the highest count of a species submitted on a single checklist from the UM-Dearborn campus during the weekly periods indicated. They show peak numbers in 2011 were much higher than in recent years (click to enlarge).




A variety of things could factor into these increased numbers, but a couple stand out, especially for the high numbers of early migrants. First, this was a La Niña year. While La Niña/El Niño cycles do not have a strong impact on our weather here in the upper Midwest (which is more influenced by the North Atlantic Oscillation), it does have a strong impact on weather where many of "our" birds winter. Namely, it was a very wet winter in much of Latin America. Wetter winters tend to have higher insect abundance, which translates into better overwinter survival for some species of birds. Thus, some species may have been more abundant this year.

Another factor could be detectability. The overall cool weather, without early hot spells, slowed leaf-out on woody plants. When trees don't have leaves, birds are simply easier to see and count. The graph below shows the accumulated growing degree days (GDD) for the period of 15 March, when woody plants here often begin to awaken, and 10 May, when we would expect many migrant bird species to be present. GDD are a measure of heat accumulation based on daily temperatures that are often used in agriculture to determine, for example, when crop species are likely to mature (data from Detroit Metro airport, click to enlarge).

As you can see, by our peak day of 10 May, the accumulated GDDs were the lower than they had been for years, which was reflected in the slow leaf-out of the trees here on campus.
Other notable birds this spring included Osprey on 10 and 23 May; five records of Bald Eagle, of which three were on campus; five records of flyover Sandhill Cranes, all from campus (there have only been 10 records in the past 10 years!); and the spate of Bobolink sightings around Dearborn between 6 and 9 May which included ten singing males in the fields at Hubbard and Southfield on 8 May.

Arrival dates
Only two species arrived earlier than any previous record for Dearborn. They were Ruby-throated Hummingbird on 26 Apr (4 days earlier) and Indigo Bunting (27 Apr off-campus, 1 day earlier). A Blackburnian Warbler on 27 Apr tied the previous early arrival date. Two Common Loons seen over east Dearborn on 20 Mar were also early, but occasionally this species winters in the Great Lakes.

Extremes are interesting, but deviation from a more typical arrival date is probably a more accurate depiction of any shift in migratory phenology. I have 14 to 21 years of spring arrival dates for 43 species. There are a number of ways to calculate central tendency (or the "expected" middle value of a data set). For simplicity's sake in this example, I calculated the arithmetic mean, or average arrival date for each species to compare to this year's arrival dates. For these 43 species:

• Fourteen (32%) arrived on their average arrival date.


• Seven (16%) arrived later than average (the average for those species only was 3 days later)


• Twenty-two (51%) arrived earlier than their average arrival date (for those species, the average was 4 days earlier).


• For all 43 species, arrival time averaged 1.6 days earlier than "usual."

All spring data from 1994 through 2011 is now in eBird. You can explore all of the survey data input for the campus at eBird. Use the "Change date" button at the top of that page to look at separate years or to compare years.

Many thanks to Darrin O'Brien and Mike O'Leary, who assisted with surveys this spring.

NAMC 2011 - Dearborn portion

Saturday, May 14 was the North American Migration Count. My husband Darrin O'Brien coordinates the count for Wayne County, and as usual we covered the UM-Dearborn campus, as well as some other spots in Dearborn. It was a pretty lousy day weather-wise, and many of the migrants that we enjoyed last week had moved on. Although we were only able to thoroughly cover campus and one of the Ford fields (with quick peeks at a few other locations) we still managed to have a pretty good day. On campus we tallied 83 species, including 19 species of warblers. None of the warblers were recorded in numbers over 10 individuals, but we had great looks at Mourning Warblers which is always a treat. Most of the warblers were feeding rather high in oak trees, typical of mid-migration as they are among the last trees to leaf out. Other highlights included a flyover Broad-winged Hawk, and the first Gray-cheeked Thrush of the season. We spent more time than we budgeted at the Ford field in the southeast corner of Hubbard and Southfield. We ended up with 48 species there, including 13 warblers species feeding in the oaks along the margins. This field, along with several others, has been planted in a cover crop of clover. While the Bobolinks present there earlier this month have moved on, there were many Savannah Sparrows on territory or with nests, along with Ring-necked Pheasant, Eastern Towhee, and some lingering White-crowned Sparrows. One of the better birds of the day was a calling Eastern Meadowlark in field #8. This is no longer an easy bird to find in Dearborn. Please note that these fields are now posted "no trespassing" so should only be viewed from public roads. RRBO has permission from Ford security to survey them. One last surprise was a big roost of Double-crested Cormorants (above) at Fordson Island. Between the birds perched on the dead tree and the ones flying around the Ford Rouge Plant, we counted 102. Back at home in east Dearborn, we had one of the Pine Siskins nesting in the neighborhood. Unfortunately, we did not have the time to walk along the Rouge River channel, or hit a couple of other birdy spots. Overall, we had 98 species (23 warbler species) in Dearborn for the day.