Wednesday, June 27, 2012

Spring 2012 survey results

The spring 2012 survey season took place 3 April through 4 June. On campus, regular surveys were conducted on 58 of the 65 days; some coverage late in the season was truncated due to field work related to our catbird study. Because of the unusual weather (discussed below), surveys were also conducted on 21 days in March.

Excluding March, the campus surveys recorded 124 species (another 19 were recorded in Dearborn off-campus). This is lower than the previous ten-year average of 130 species. The peak day was 3 May with 79 species. This is a similar to our usual peak day total of 80 species, but usually the peak occurs much later in the month (around May 16-20). Both the low species totals and early peak are at least in part attributable to the extremely early leaf-out, which made visual detection of mid- and late-season migrants much more difficult.

This leaf-out -- in which leaf and flower phenology was some five weeks ahead of schedule by April -- was due to the unprecedented hot weather in March. The National Weather Service characterized March 2012 as the warmest on record and the most unusual month in Detroit's history. The average temperature for March was 50.7 F, an incredible 15.6 degrees above the 1874-2011 mean average of 35.1F! Fortunately, the weather did cool down, with April temps right at normal, but May was the 3rd warmest on record. Thus, spring 2012 finished the warmest in southeast Michigan history.

Generally, warm periods in spring that accelerate plant growth also prompt early emergence of insects. This can result in a mis-match between insect resources and the timing of bird migration, especially for birds that are coming from wintering grounds in the tropics. These birds are prompted to migrate by changes in day length, and do not "know" that spring is advanced in the north. The same weather systems that bring warmth to the north may push migrants which have already arrived in the United States northward a little faster. This year, long-distance migrants that had yet to arrive during the early part of the season arrived right about their usual time (see Arrival dates, below).

There were some real concerns that had the hot weather continued, things would have gotten seriously out-of-whack -- you can read my blog post What does summer in winter mean for birds? for a discussion of potential ramifications. Fortunately, cooler weather in April slowed phenology down a bit. While we did have freezing overnight temperatures after the March hot spell, they did not last for many hours in the Detroit area, so insect life was not seriously diminished and it appears that migrants were able to find adequate food resources.

Spring 2012 was also quite dry...especially when compared to last year! In 2011, the precipitation total for Detroit from March through May was over 14 inches. This spring, it was less than half of that, with both April and May having below-average moisture.

While migrants dodged a resource bullet, it seems this combination of advanced plant and insect phenology and dry conditions is likely to have had some impact on breeding birds. This probably depends on how reliant various birds are on particular stages or species of insects as well as the impact weather may have had on a very small landscape scale at locations where birds nested. Perhaps we will detect some changes in the ratio of young to adult birds during fall banding that may shed some light on this. Finally, because they flowered early and pollinators were out and about, many fruiting plants also set fruit early. Fruit is a critical part of the diet of many fall migrants; we'll see if there are any changes in what birds are eating this fall.

Many of the less-common migrants we have come to expect on a nearly annual basis were not recorded this year. This includes Golden-winged Warbler, Prothonotary Warbler, Kentucky Warbler, and Summer Tanager. Acadian and Olive-sided Flycatchers and Philadelphia Vireo were also missed. The most interesting highlight was the number of White-eyed Vireo sightings: five from mid-April to mid-May. Leaf-out was so advanced by mid-May, that many birds, especially non-singing females, may have gone undetected.

I'll add a lowlight on a species I follow and mention frequently: American Crow. Of the 61 days in April and May, crows were recorded in the entire city of Dearborn on only 15 days. Reports were always of one or two birds. Crows were seen more often in March, as observations include migrating birds. In March, crows were reported on 14 days, mostly in ones or twos, with a high number of 11 birds in a flock on 13 March.

Arrival dates
The March hot spell created a flood of reports of early migrants. Many of these are probably best viewed with caution (see my post Early Neotropical migrants for more discussion). Of the 43 migrant species for which we have adequate reliable arrival data, 31 did arrive earlier than the average date calculated through 2011. Both the median and the mode for the number of days early for these species was 2 days. Thirteen species arrived four or more days earlier than average. A few short-distance migrants had record-early dates for Dearborn:
  • Tree Swallow on 18 March, previous early date 22 March
  • Field Sparrow on 18 March, previous early 24 March
  • Chipping Sparrow on 26 March, previous early 30 March
Of the long-distance migrants, new records were:
  • Nashville Warbler on 16 April, previous early 20 April
  • Canada Warbler on 4 May, previous early 5 May
So, nothing particularly outstanding. Many thanks to Darrin O'Brien who assisted with surveys this spring.

Wednesday, June 20, 2012

Dickcissels in Dearborn

(Edited 25 Jun with new data)
There are at least a dozen Dickcissels (maybe more) in the wildflower fields at Ford Road and Mercury. This is the field marked "8" on our page of Ford fields. Note that the fields are marked "No trespassing," so if you visit, please scan from a roadside and be careful of traffic. I first heard these birds on 18 June. My husband Darrin O'Brien saw a bird carrying food later that day, indicating that they are probably nesting. Our survey on 24 June located at least 10 singing males and 2 females. There are also dozens of Savannah Sparrows in this field.

On 20 June, Jim Fowler and Dave Washington located two more Dickcissels in the fields on the south side of Lundy Parkway (field number "6"). Darrin had 9 there on 21 June, and we had eight on 24 June.

The two small wildflower fields ("1a" and "1b") have two birds. So, at least around two dozen Dickcissels in Dearborn!

The last Dickcissel record in Dearborn was from 1 July 1907! The only other confirmed record I could find when researching my book on Dearborn birds was a flock near the Rouge River from 30 July 1899. Three of these birds were collected, and I have examined the specimens in the University of Michigan Museum of Zoology in Ann Arbor. All of these records are attributed to "Springwells." Dearborn's present borders were established in 1929; prior to that portions were known as Fordson and/or Springwells. I believe the 1907 record was from somewhere near what is now Rotunda and Schaefer in Dearborn. The route of the Rouge River has also been altered since 1899, but I think that the 1899 specimens are also from Dearborn.

Long time, no see! The last Dickcissel record from Dearborn was in 1907.This male, 20 June 2012.
Photo by Cathy Carroll, used with permission, all rights reserved.

Female Dickcissel, Dearborn, 20 June 2012.
Photo by Cathy Carroll, used with permission, all rights reserved.

Dickcissels are specialist birds that depend on grasslands. They are known for their unpredictable, semi-nomadic movements, in particular outside of their core prairie habitat in the Great Plains. It's hard to know where they'll show up from year to year.  While they can be quite adaptable and will use non-prairie grassland habitats, the loss of native prairie has been a factor in dramatic population declines. These little birds winter far into South America, mostly in the grasslands of central Venezuela. They winter in huge flocks and can be considered pests on grain farms. They are hunted and poisoned regularly, which no doubt has contributed to declines in their numbers.

The wildflower fields the Dickcissels are using have a high diversity of herbaceous plants which are required by the birds for song perches and nesting substrate. In the great photos above, by Cathy Carroll, the birds are perched on Gray-headed Coneflowers  (Ratibida pinnata), a wonderful native wildflower. The wildflowers also provide for a wide diversity and abundance of insect prey, especially grasshoppers and butterfly and moth larvae, which are needed to raise their young.

Many of the fields planted by Ford Motor Company are sunflowers or hay fields. Those that have wildflowers are the least manipulated by mowing or disturbance and have the most interesting birds. Perhaps this will encourage Ford to convert more of the fields to wildflowers!

Monday, May 21, 2012

Catbird success!

One of our research projects at RRBO is a joint project with Dr. Melissa Bowlin, a faculty member here at UM-Dearborn. Last fall, we placed light-level geologgers (or geolocators) on a sample of Gray Catbirds on campus. Catbirds are one of our most frequently banded birds. These tiny devices measure light several times daily. If placed on a migrating bird, they will record data that can be used to calculate latitude and longitude when compared with sunrise and sunset times and light levels at noon in different geographic locations.

This data can give us a wealth of information on the pace and route of migration, and wintering areas. You can read all about how they are used on the RRBO web site. 

There is a catch (pun fully intended). In order to get the data, the bird must survive a full migration, return to the original banding location the next year, and be recaptured so the geolocator can be removed and the data downloaded. Last fall, we placed a colored leg band on each of the catbirds which also carried a geolocator, so we could more easily re-find any birds that returned this year.

Well, I couldn't have been happier to find one of our color-banded catbirds singing right behind the Environmental Interpretive Center (EIC). Once I was sure he was going to stay put, I set up three nets between two of his favorite singing perches. While I was setting the nets up, I caught a catbird I presumed might be his mate. It was banded, and turned out to be a bird we banded as a hatching-year bird in August 2008.
Nets set up on either side of the driveway to the rear of the
Environmental Interpretive Center. Hard to see? Good!
Very early the next morning it was time to try to catch "the" bird, and Dana Wloch and Darrin O'Brien joined me. Often, territorial male birds will investigate another singing individual of his own species. We placed an iPod playing a loop of a singing catbird behind one of the nets. Sometimes that's enough, but it usually helps to have a stuffed "singer" near the recording. I didn't have a stuffed catbird handy, but I did have a study skin of a European Starling.  He'd have to do.

Vulgaris the Starling Dummy. iPod playing a catbird song in the background.
Once we were set up, it was step back and wait. Our target catbird began singing, and he came in closer to the nets to investigate. Within minutes he swooped over one net, and over the next. Then again. And again. Uh-oh. These nets are kind of hard to see, but it looked like our bird had figured out our ploy and was avoiding them.

Dana and Darrin, dejected. We thought we were in for a long morning.
After about 10 minutes, the catbird flew from behind one net headed back to his usual singing spot and ventured a little too low. Bingo! In the net. We quickly retrieved him.


It didn't take long to take him into the banding lab, remove his geolocator and green band (so we didn't go after him again), and take some measurements so we could let him go.

Three happy catbird catchers, and the subject ready to be released.
This catbird, which was carrying geolocator #929, was the last catbird we put a device on last fall, on 29 September 2011. The bird had originally been banded as an adult on 10 August 2010.

The well-traveled geolocator.

Dr. Bowlin is out of state on another field study, and when she returns she will download the data from the device. Then, it will take some additional time to analyze. Sometimes due to weather or time spent in shaded spots by the birds, the data may difficult to interpret. Hopefully, we'll get good data from this bird, as well as any other catbirds that return that we recapture.

And we have already located the favorite singing perch of another color-banded catbird. I hate to report that we have tried catching this bird for several days and have come pretty close, but so far he seems to be on to us and prefers singing about 10 yards from the nets. We also have a tentative sighting of a third bird, and have some areas left to survey for catbird pairs. I'm optimistic we will be able to retrieve a few more geolocators this season.

About half of our catbirds were sponsored by donors last fall. Unfortunately #929 did not have a sponsor, so we didn't get to provide fun news to one of our supporters. If you are interested in sponsoring a catbird with a geolocator, I'll assign one to anybody making a gift of $300 or greater.

Wednesday, May 16, 2012

North American Migration Count 2012

The North American Migration Count takes place the second Saturday each May. It aims to take a "snapshot" of migration, and is compiled on a county basis. My husband Darrin is the coordinator for Wayne County, and as usual we covered the city of Dearborn together on May 12.

Spring migration this year got off to a great start the first week in May. We had very good numbers of early migrants the last week in April into the first week in May. There was a nice influx that included some mid-season migrants on May 3. Within a few days, however, things began to slow down. On migration count day, we tallied a disappointing 70 species on campus. Warblers in particular were very scarce, with only ten species. Yellow-rumped Warblers had been dwindling, but were absent on count day. Many people commented on the high numbers of White-crowned Sparrows this season, but on count day we had only a few, and no White-throated Sparrows. Our best bird on campus was a Gray-cheeked Thrush, the first of the season.

Darrin taking a quick break on campus during the count. Sometimes,
having too few birds is more tiring than having too many!
We added eight more species at other locations in Dearborn. The original Ford "sunflower field" at Hubbard and Southfield had a minimum of two dozen Bobolinks on May 7, but none stuck around for the count.

The Rouge River at Kingfisher Bluff behind Henry Ford
Community College.
Northern Rough-winged Swallows are nesting in the terra cotta
tubes poking out of the bank at Kingfisher Bluff behind Henry
Ford Community College.
The best bird of the day was an Orchard Oriole at Porath (Kielb) Park. This 11-acre property in a sparse residential area adjacent to railyards and an industrial border of Detroit was once a clay mine for bricks. In the 1940s, fill material from construction of I-94 was added. A federal brownfields grant was used to clean up contamination (still no digging allowed, according to warning signs) and it was turned into a park by the city in 2005. There are a variety of native plants there, but aside from a trail that is mowed through it, the park has not been maintained very well and it's becoming weedy and overgrown.

In addition to the oriole, Porath had two very good butterflies. One was a Common Checkered-Skipper (Pyrgus communis), a southern species that has been seen in southern Michigan with increasing frequency the last few years. Not only is this an uncommon species, this is a pretty early date to see them here. It's unlikely that the larvae (the stage in which they hibernate) can survive here overwinter, so the individuals we typically see are migrants from the south, or perhaps some progeny from these migrants which appear later in the season. Their host plants are in the mallow family, and I have seen them most commonly in vacant lots or neglected fields that are infested with velvet-leaf (Abutilon).

Here is my bad documentary photo of a Common Checkered-Skipper at
Porath Park. Click here for a much nicer shot of one in my Dearborn yard last fall.
We also saw another uncommon butterfly, an "Inornate" Common Ringlet (Coenonympha tullia inornata) When we found our first county record in 2003, it represented a substantial southern range expansion in the state (PDF of my note in the newsletter of the Michigan Entomological Society here). This species now shows up all over the place in southern Michigan, moving south here as it has in New England and Ontario in the last decade or so. I failed to get a photo, but here's one Darrin took last fall in Oakland County.

Both the skipper and the ringlet have been observed on the UM-Dearborn campus as well.

A table of results from the Wayne County North American Migration Count, with links to complete results, is available on the RRBO web site. Once we have data from all the other field participants, I'll put up the 2012 results at that location as well.

Monday, May 7, 2012

Chimney Swift tower!

Chimney Swifts are probably familiar to most people: twittering "flying cigars" in our summer skies, feeding on aerial insects. Like other species of swifts, Chimney Swifts spend most of their time in the air, even mating and bathing on the wing. Chimney Swifts breed across much of eastern North America, and winter in the Amazon basin of northwestern South America.

Patient observers might note individual birds disappearing into tall chimneys during the breeding season. Chimney Swifts make a small nest of twigs, held together and glued with saliva to the inside wall of a chimney-like structure. Only one pair will nest per chimney or structure, but there may also be a few non-breeding swifts, some of which (usually young from a past year) may "help" the breeding swifts feed the young in the nest. Chimney Swifts use chimneys and similar structures outside the breeding season, too. During migration, especially in fall, many hundreds of swifts might use large chimneys to roost in overnight.

Prior to European settlement of North America, Chimney Swifts used hollow trees, caves, and narrow chasms. Their populations probably increased with the availability of human structures for nesting and roosting. However, in recent years Chimney Swift populations have undergone a dramatic decrease. In the U.S., this decline has been about 2.4% per year since the early 1980s; in Michigan the rate has been -1.5% annually (based on Breeding Bird Survey data).
Several factors are probably at play. Most important is a decrease in aerial insect prey, likely due to pesticide use, habitat loss, and a changing climate. Other species of birds that rely on aerial insects, such as Common Nighthawks and swallows, are also on the decline. Add to this a special problem for Chimney Swifts: chimney design has changed in modern times, with many chimneys being too narrow, or covered or lined, for swifts to use.

This has led many organizations and individuals to create artificial Chimney Swift nesting structures. This spring, Stephen Lisius constructed and erected one of these excellent towers behind the Environmental Interpretive Center as his Eagle Scout project.

Stephen designed the tower according to plans similar to the graphic above, which is available in the Chimney Swift Nest Site Research Project Information Handout (PDF). The tower was constructed off-site, and then erected onto a sturdy foundation that had been put in place the week before. Here's the tower in place:

The outside of the tower will be finished soon with weatherization wrap and shingles. Stephen also plans to install a camera, so if/when swifts discover and use the tower, we can see what's going on. We may have to be very patient -- some towers go for years before they are used. I'll keep you posted!

If you are interested in learning more about these towers or even seeing if you'd like to make one yourself, the book Chimney Swift Towers: New Habitat for America's Mysterious Birds is the go-to guide.

Meanwhile, you might consider one of the swift monitoring projects. The program called Swift Night Out is done each fall in the U.S. Bird Studies Canada has initiated a citizen swift monitoring program as well.

Chimney Swift photo by D. Irving under a Creative Commons license. Tower photo by Sara Cole, used by permission.