Wednesday, July 1, 2015

Grasshopper Sparrows nesting in Dearborn

On 26 May, long-time RRBO volunteer and contributor Mike O'Leary found several singing Grasshopper Sparrows in the vacant lot at Rotunda and Southfield. This lot was once the site of some Ford Motor Company buildings, which were torn down around 2003. It is now managed by the Oakwood Physical Therapy & Wellness Center. Even after all these years, the footprint of the old buildings on the easterly portion of the property closest to the Southfield Freeway and service drive can be seen.

Up to four singing males continued at the site in June. Grasshopper Sparrows are considered a Species of Special Concern in Michigan, a status just below the legally-protected status of Threatened. In addition to a significant population decline statewide, surveys have shown that their numbers have decreased 4% annually in Michigan from 1996-2007. During the Michigan Breeding Bird Atlas period in 2002-2007, Grasshopper Sparrows were only confirmed nesting in one western township in Wayne County. While Grasshopper Sparrows probably nested in Dearborn at some point prior to 1900 or so, there have been only a handful of records of spring migrants since the 1970s, and just one summer record of one individual. These territorial birds represent the first likely nesting in the city in modern times.

Low grasses and taller forbs (mostly sweet clovers, Melilotus ssp., and fleabanes,
Erigeron ssp.,) in the area favored by the sparrows.

Not all grasslands or fallow land is equal to the various species of grassland birds. Grasshopper Sparrows have a strong preference for habitat that is mostly grasses and forbs (herbaceous weeds) which are not densely distributed, interspersed with bare ground (up to 20%), and few or no shrubs. The portion of the site that once had buildings on it have numerous patches of bare ground or sparse vegetation on the former building footprint, and most of the sparrows have been found there.

Patches of bare ground are required by Grasshopper Sparrows.
Because it is adjacent to the freeway, the insect-like song of the Grasshopper Sparrows are very difficult to hear! The field is also full of dozens of nesting Savannah Sparrows, Red-winged Blackbirds, and Killdeer, among other species. They make quite a ruckus, but we believe there are still likely up to four singing male Grasshopper Sparrows and, due to their duration at the site and the persistence of the location of at least one of the males closest to the parking lot, they are likely nesting. Because we do not want to risk stepping on the ground nests of any sparrows or disturbance to any birds, we've restricted our regular surveys to the edge of the property after I made one thorough walk-through. After I notified Oakwood of this special bird, they instantly stepped to the plate and made plans to postpone any mowing of the field until August, after any young should be fledged and independent.

We will be keeping an eye on the sparrows to see if we can catch them feeding young in the next few weeks. Many thanks to Oakwood for the stewardship of these special birds.

Thursday, March 5, 2015

Winter Bird Population Survey 2014-2015

The 23rd year of RRBO's Winter Bird Population Survey has been completed. December started out pleasantly but the survey season ended with a snowy and bitterly cold February. Weather aside, it was a fairly average year. The 14 survey days over the late December to late February period was typical. Surveys totaled about 23 hours, which is 6 hours below the 29 hours that are average, but represent the shortage that took place on our Christmas Bird Count day.

The 34 species tallied was a little below the 22-year average of 38, but can be partially explained by some habitat changes and restrictions. Access to the Rouge River behind Fair Lane Estate was greatly restricted due to being fenced off for riverbank restoration; vegetation along this area also removed. The river was frozen much of the period, and no waterfowl were counted after January 1. No Belted Kingfishers were recorded; they have only been completely missed on a few other counts.

Heavy construction activity along Fair Lane Drive also impacted bird activity along eastern edge of survey area. This construction will be continuing through summer, and likely also have an effect on spring surveys.

Eleven species were found on all 14 survey days. In descending order of abundance they were: House Sparrow, House Finch, Northern Cardinal, Blue Jay, Black-capped Chickadee, Dark-eyed Junco, Downy Woodpecker, White-breasted Nuthatch, Tufted Titmouse, Red-bellied Woodpecker, and Hairy Woodpecker -- all feeder birds.

Despite the availability of feeders, most sparrows were recorded in numbers well below average. Only a single Song Sparrow was recorded, while the previous season total average is 13. One or two American Tree Sparrows were recorded several times, but the previous season total average is 34. White-throated Sparrows have been common winter residents here, especially over the past decade. A total of 25 were counted this year, with an average per survey of 1.7, the lowest numbers since 2002. The previous 22-year means were 80 per season and 6 per survey; these averages since 2003 were 157 and 9. Juncos were also counted in below average numbers, although not as drastic. I'm not sure exactly what might have contributed to the depressed numbers of ground-feeding seed eaters, except that a lot of understory vegetation has been removed and perhaps there is less cover.

Fruit-eating birds were largely absent. No Cedar Waxwings, Hermit Thrushes, or Yellow-rumped Warblers were recorded. Most days there were no American Robins present, the maximum number on a survey day was 3. This represents the second lowest number of American Robins in 23 years. Fruit-eating species were generally scarce on local winter bird counts this winter, so it's hard to tell what impact the removal of fruit-bearing non-native trees and shrubs that was undertaken by the university may have had on these numbers.

The highlight was probably the Pine Siskins that were present in small numbers through mid-January. They moved on from here (and other places locally) and had not moved back through on their way north by the time the survey period ended. This was the only one of the "irruptive" species present on campus this winter.

All the numbers from this year are on the RRBO web site, along with past counts and the history and methodology of the survey.

Monday, March 2, 2015

Dearborn adds another new species!

On 1 March 2015, Larry Urbanski found a Long-tailed Duck (Clangula hyemalis) in the Rouge River near the Ford Rouge Plant. There is a photo attached to his eBird checklist (sign in may be required for one or both links) and the bird appears to be a male.

Mike O'Leary and I attempted to locate the bird this morning, and found a Long-tailed Duck that appears to be a female, or at least doesn't look like the bird found yesterday. In the photo below, it's the bird on the left, next to a Red-breasted Merganser. I should be able to post some better photos later.

Long-tailed Duck is the 260th species on the Dearborn list.

Most of the Rouge River is still frozen solid. The areas in the Ford Rouge boat slip and adjacent waters stay open all year. Other waterfowl present included a couple hundred Common Mergansers, at least 24 Red-breasted Mergansers, Canvasbacks, a few Ruddy Ducks, Common Goldeneye, Redheads, and Greater Scaup. There were at least 20 Great Black-backed Gulls -- a species not recorded in Dearborn until 1987. Ten sort of miserable looking Great Blue Herons hugged the shoreline, as did 10 Black-crowned Night-herons. There is a small pond inside the plant next to the river that accepts warm-water discharge from one of the steel mill facilities, and a bunch of night-herons have wintered there for years.

Many thanks to Larry Urbanski for this great find.

Saturday, January 10, 2015

Dearborn portion of Detroit River CBC, 2015

The Detroit River Michigan-Ontario Christmas Bird Count was held, as it is each year, on January 1. This was the 37th year for the count, which is centered at I-94 and Warren Ave, and the 21st year that RRBO has coordinated the field work in the city of Dearborn.

The skies were fair, but the temperatures were cold and windy. This was the first real cold snap of winter after a very mild fall and December. It was cold enough to freeze up a lot of water, but as count day was only a few days into the cold snap, it had not really been cold enough to push a lot of regional waterfowl into the always ice-free areas in our count circle. For example, this was onlly the second year that Canvasback were not counted; in fact, Common Merganser was the only diving duck recorded this year.

Unfortunately, our two counters on campus had unexpected family obligations, resulting in the best remaining habitat in the circle being under-covered. We had the lowest number of party-hours in our history, and raw numbers of many species of common birds were record lows, but not really reflective of actual populations. For these species, the Winter Bird Population Survey will provide more accurate numbers.

The obvious highlight of the count was a Lesser Black-backed Gull, found at the Ford Rouge Plant by Jim Fowler, Mike O'Leary, and Dave Washington, and photographed by Dave.

Most years this team is able to get special permission to enter the complex and check out the open water in the boat slip and other areas not visible from outside the plant. This is the third Dearborn record for Lesser Black-backed Gull. The others were also at the plant, in January and December 2004. This brings the cumulative total for the Dearborn portion of the count to 88 species.

Fifteen Black-crowned Night-Herons were also in their usual wintering spot around an awful little pond in the plant (described in the 2011 post). Most Black-crowned Night-Herons move south for the winter, but a few stick around coastal spots in the Great Lakes.

A view of the Rouge complex from the Dix Street bridge. Urban birding, anyone?

The usually-productive Ford "sunflower" fields mostly lacked birds this year. The only one with sunflowers was at Ford World Headquarters, where we did have 48 Red-winged Blackbirds and many House Sparrows and American Goldfinch. However, all the sunflower heads were seedless. The fields at Hubbard and Southfield, usually the best, had been planted in hay and harvested. Not even weed seeds were evident.

One field had a few rows of sunflowers at the edge, but they were stripped and had no birds.

As usual, we had a Peregrine Falcon at the Ford World headquarters and vicinity, and another one heading north up the Rouge River behind Henry Ford College. There have been two reported off and on this winter in the area.

A male Ring-necked Pheasant that we flushed at Porath Park was the first on the count in 11 years. Porath (Kielb) Park is an 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 (although not this year, apparently), the park has not been maintained very well and it's becoming weedy and overgrown. Still, we like to go take a look each year.

Everyone familiar with this count and our winter bird surveys knows that Dearborn has not seen its American Crow population recover since it was decimated by West Nile Virus -- my most recent summary is here. For this count, we've only counted 1-3 the last few years and this year it finally happened: no crows for the first time in the history of the count.

We ended the day with 38 pecies, which is a record low.

The complete results of the Dearborn portion of the 20145Detroit River CBC can be found at the RRBO web site, which includes historical results. I've written summaries here at Net Results for the 2014, 2013, 2012, 2011, 2010, and 2009 counts.

You can read an analysis of the first 25 years of the overall count in this paper:

Craves, J. A., and J. A. Fowler, Jr. 2003. Twenty-five years of the Detroit River Michigan-Ontario Christmas Bird Count (pdf). Ontario Birds 21:109-128.

Tuesday, November 18, 2014

Fall 2014 fruit and seed work

I mentioned in a previous post that our analyses of seeds found in the fecal samples of birds requires context: some sort of compilation and rank abundance of all the ripe fruit available to birds to eat when they are present in the area. In that post, I described our fruit counting methods.

Fruit morphology
Another aspect of our work this fall was describing various morphological characteristics of the common species of fruit available at our site. Many factors go into fruit choice by birds. Among them are the size of the fruit, how many seeds it contains, and the size of the seeds.

Some of these data are available in the literature. As I searched for these metrics, I found that for some species different sources reported quite different numbers, some sources had data on one characteristic but not others, while measurements for some species were not to be found. The best, though not the easiest, solution was to take measurements ourselves. Weekly, we collected around 10 fruits from each of around 30 species, measured the fresh fruit, counted the seeds per fruit, and measured the seeds. Dana Wloch started this project last year, and it was expanded this year. I'll be finishing up with some of the late fruiting species next week, but so far we have measured about 3300 fruits and over 7000 seeds!

Some of our results are basic. For example, the average diameter of the five most common seeds in fecal samples (Common Buckthorn, Amur Honeysuckle, American Pokeweed, Riverbank Grape, and crabapple) is 8.2 mm. This agrees with other studies that have shown bird-dispersed fruits typically average about 8 mm.

Some results are much more intriguing. Glossy Buckthorn is a non-native species that can be quite invasive, especially in wetlands. A recent study from its native range in Sweden stated the average diameter of the fruits was 8.7 mm (458 fruits) with an average of 1.7 seeds per fruit. We measured 134 fruits here over two years, and the average both years was 7.7 mm. The average number of seeds for 168 fruits was 2.5.

Glossy Buckthorn fruit does not ripen simultaneously, so red,
unripe fruit are often on the same branch as black, ripe fruit.

Glossy Buckthorn has been shown to have evolved different morphological characteristics in different parts of its native range. This species has been present in North America for over 200 years. If our data is truly representative of the local population, it might suggest adaptation to a different suite of dispersers, exposure to more or better pollinators, and the higher seed set may be a factor in its success as an invader. All speculative at this point, but no doubt it will prompt me to continue measuring Glossy Buckthorn!

Seed samples
Meanwhile, during the fall season, we collected 453 fecal samples from 6 bird species. However, over 80% of the samples were from robins that we did not band. Several years ago, the University began cleaning off all sidewalks and roads on a daily basis in fall. In a number of areas, low spots in the pavement hold water and attract robins, which often then "leave a deposit." Collecting these samples in communal bathing and drinking areas, as well as along other paths where we observed robins foraging on the ground, is a convenient way to acquire a lot of data.

For catbirds, the top four species in our 41 samples this fall were:
  • American Pokeweed (native)
  • Riverbank Grape (native)
  • Amur Honeysuckle (non-native)
  • shrub dogwoods (native)
This closely follows the rankings for the 5 previous years combined. Pokeweed and grape have ranked #1 and #2, while the shrub dogwoods have been #3 and Amur Honeysuckle and Glossy Buckthorn are close together at #4 and #5.

Sample sizes for robins are much higher. This fall the 453 samples revealed the top four species as:
  • Amur Honeysuckle
  • Common Buckthorn (non-native)
  • crabapples (non-native)
  • Riverbank Grape
These four species are also the same top four species from over 900 samples from previous years, although Common Buckthorn has been the top ranked species for those 5 years.

Two other species in robin samples were notable. Previously, Multiflora Rose (non-native) was found in 4% of samples; this year it increased to 6%. This is interesting considering a number of Multiflora Rose has been reduced in the past year or so both by removal and from infection by rose rosette disease. We also have the native Illinois or Climbing Rose (Rosa setigera) here. There is overlap in the appearance of seeds of these two species, but there are fewer R. setigera, their hips are larger and "ripen" later than multiflora. I believe most of the seeds found in fall samples are probably multiflora.

A comparison of the large hips of the native Rosa setigera (left) and the
small hips of non-native Rosa multiflora (right).
Asiatic Bittersweet (non-native) was previously found in less than one percent of samples. This year, it was in 5% of samples, a rather large jump. This species has also been the target of removal the last couple of years. The capsules encasing the fruit usually open fairly late in the season, and did not seem much earlier this year (first date in samples Oct 8) than the average (Oct 16). Thus, neither increase in the number of plants nor early fruiting seems to explain the higher proportion of samples with bittersweet.

Asiatic Bittersweet is especially conspicuous when there are no leaves on trees.

One possible explanation for the increase in these two species is that robins are eating more of them because a great deal of their top-ranked species (buckthorn and honeysuckle) have been removed in the larger landscape.  However, annual fluctuations due to weather and crop size can be large, so it will take more years of sampling to see if this year was just a quirk, or if trends will start to appear.

I haven't done much digging through the numbers yet, but even this quick look is pretty interesting.