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.

Spring migration update

Spring migration has been terrific the last week, so I hope everyone has had a chance to get out and see some birds. I thought I would provide a more detailed update here.

The chart below shows the number of species seen on campus each day since 2 May (the yellow line) as well as the number of warblers species (the blue bars). Click to enlarge.

The best day of the season was 10 May, with 95 species recorded, 25 of which were warblers. For some perspective, there are 37 species of warblers that occur regularly in Michigan (4 more are considered accidental; we have recorded all but 2 of the 41 species in Dearborn in the last 40 years). Some of the warbler highlights were a Kentucky Warbler on 10 May, our first record since 2006 of this southern species, and a female Prothonotary Warbler, which was present from 9-11 May. A gorgeous Golden-winged Warbler was also seen from 10-12 May. Closely related Blue-winged Warblers have also been present, while on 8-9 May, a hybrid of the two, a "Brewster's" Warbler, was observed; it sang a Blue-winged song. The total number of warbler species for 2011 so far is 28.

Other bird highlights of this period include a Summer Tanager and an Osprey on 10 May; a fairly early Olive-sided Flycatcher on 12 May, and two Red-headed Woodpeckers on 13 May.

We have recorded 133 species on campus so far in 2011. The total for Dearborn for the year is 151. This includes two records of Clay-colored Sparrow. One was this bird, photographed by Cathy Carroll along the Rouge River near the TPC of Michigan on 10 May.

Another was singing at the fallow sunflower field at the south side of Hubbard at Southfield. That location also hosted up to 10 male Bobolinks from 6-8 May.

I think migration has been terrific due to a combination of things. First, we did not get the very early warm spells that we have had the last couple of years, so trees and shrubs did not leaf out early. This has made viewing conditions quite excellent. Cool mornings have concentrated birds in sunny spots in the morning, and also resulted in many insects being most abundant near the water's edge (on campus, along Fairlane Lake). Thus, birds have been easier to find. Some credit has to be given to the luck of weather patterns, which are always the wild card. Finally, I think we are recovering from population losses that were due to the dramatic cold spell in the eastern U.S. in spring 2007.

There is a lull right now, but I expect we will get one more good wave of migrants before the end of the month. Viewing conditions will be more challenging now that foliage is thicker, but do your best to get out and enjoy!

Update on the Ross's Goose

In my last post, I described the discovery of a Ross's Goose on 24 March 2011, a first record for Dearborn. The goose was banded, and we have just received the details from the Bird Banding Lab.

This was a nestling male banded on 7 August 2006 in Nunavut. This much I knew from reporting the goose on the Bird Banding Lab's web site. The location, it turns out, is McTavish Point. The geocoordinates are 67.75, -101.08333, which places it north of the Arctic Circle in the Queen Maud gulf region, where over 90% of the world's Ross's Geese nest.

This map (click to enlarge) shows the banding location with a red marker: this is 1900 miles in a straight line from Dearborn. I've also indicated the location of Akimiski Island in James Bay, Nunavut. Although we do not see many Canada Geese with orange neck collars around here any longer, this is where nearly all of them were banded.

Ross's Geese have undergone a substantial population increase in the last few decades, and while once exceedingly rare in the Midwest and eastern U.S. during migration and winter, they have been showing up in these regions with increasing frequency. The increase in Arctic-breeding geese (especially Snow Geese) has profound impacts on sensitive habitats. "Our" Ross's Goose was banded by Ray Alisauskas, a scientist with the Canadian Wildlife Service, one of the key researchers working on the status of Ross's Goose and Snow Goose and their impacts on Arctic ecosystems. (Thus answering the obvious question of who would be in such a remote place banding geese!)

Most of the specific information on the winter or migratory distribution of Ross's Geese based on band recoveries is from hunters. Presumably, a report like ours, from a live bird, is quite rare.

While not the flashiest bird, this Ross's Goose surely had one of the most interesting stories of any bird we have encountered!

New for Dearborn: Ross's Goose

In the late afternoon of 24 March, Jim Fowler, Jr. found an adult Ross's Goose on private property, a first record for Dearborn. Several of us were able to see the bird and get some photos, and were hopeful the bird would be present in a more accessible area the next day. Searches all over the city turned up empty, however.

The goose was in the company of three Canada Geese, and was approximately the size of a Mallard, perhaps slightly larger. In Mike O'Leary's first photo, the bird is relaxed and shows the short-necked appearance of a Ross's Goose (it later got a little wary and raised its head a lot). The feathering between the bill and face was very straight, and the base of the bill had the characteristic blue-gray color and the some of the warty bumps of a Ross's Goose. (These warts are most pronounced on older males, least on females.)

Looking at the bird with binoculars, no grin patch was readily apparent; in the close-ups of Cathy Carroll's photos below, a thin dark line is present. This seems to be within the range of an "acceptable" Ross's Goose. The forehead didn't appear as "steep" as some Ross's Goose photos I have seen, but is also within the range for Ross's. It was obviously not a Snow Goose, but many of these geese have been judged to be hybrids.

We all appreciated (and enjoyed!) Cathy's belly-crawl up to the goose for a few closer photos.


The last two are the same photo; I increased the contrast of the second photo.

Those of us who saw this goose feel pretty comfortable calling it a Ross's Goose, and not a hybrid with a Snow Goose. According to the Birds of North America account for Ross's Goose, the percentage of hybrid Ross's x Lesser Snow Goose was 1.9% between 1989 and 1992 (n=2,943 Ross’ Geese captured) during banding operations in central Canadian Arctic. This was down from 4.7% for the period between 1962 and 1968 (n=29,880). It sure seems like many more birds are called hybrids than are likely to be actually present in the population. Perhaps this speaks to our lack of ability to truly distinguish the species of some intermediate-looking birds.

A final clue is available that may corroborate the identity of this goose. It had a band on its left leg. We have several photos that show most of the numbers, and I have a call into the Bird Banding Lab to the person in charge of looking up partial band numbers.

UPDATE: We have confirmed that this is indeed a Ross's Goose, banded in Nunavut on 7 August 2006, a male of unknown age.

This is the 257th species for Dearborn. There are fewer than 6 records of Ross's Goose for Wayne County.

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Thanks to Joe Hildreth for his comment below noting that a banded Ross's Goose was seen in Bowling Green, OH from 13-19 March. The pitch of the forehead, feathering near the bill, and bill structure look strikingly similar to the Dearborn bird. There is a link in the comment to a couple of photos.