Monday, November 5, 2012

White-winged Crossbills

FPR-2012-11-04-59.jpg FPR-2012-11-04-31.jpg FPR-2012-11-04-72.jpg FPR-2012-11-04-63.jpg

White-winged Crossbills on hemlocks near Kingsley Park, November 4, 2012. An unusual bird for this area. Part of a wider incursion (or "irruption") this year of crossbills and other finches that usually winter much farther north. What's neat about this influx is that scientists predicted it.  Periodically, northern conifer forests have low seed crops over large geographic areas.  In seed-poor years, finches have to travel farther south than usual to find enough food.  So this is an ecology-based prediction: because of low food resources the birds have to expand their winter range (and/or switch food resources), with the energetic tradeoffs that involves.  White-winged Crossbills are specialists on the small, tight cones of spruce, mainly. But when they wander into the range of Eastern hemlock, they will stop at hemlocks for a meal.  

Look at this remarkable contrast between last year and this year: 

2011 vs. 2012 White-winged Crossbill sightings in eBird

Aug-Nov 2011
(good seed-crop year in Canada)

"This winter's theme [2011] is that cone crops are excellent and extensive across much of the boreal forest and the Northeast. It will not be a flight year."

Aug-Nov 2012
updated Nov 14 (last 30 days marked in orange)

(poor seed crop year in Eastern Canada)

"The theme this winter is that each finch species will use a different strategy to deal with the widespread tree seed crop failure in the Northeast."   --Ron Pittaway, Winter Finch Forecast, 2012


Monday, October 29, 2012

Barred Owl at Black's Nook


October 27, 2012.  Five yards off the path to Concord Ave.  More here.

Monday, August 13, 2012

Boston’s “Other Emerald Necklace”?

In June and July and August, volunteers reported four species of herons at Fresh Pond’s Black’s Nook: Great Blue Heron, Great Egret, Green Heron (at least six individuals), and Black-crowned Night Heron (at least four, including two juveniles). Green Herons have been present since May, and with the late-summer appearance of juveniles we seem to have collected good evidence that they have probably nested successfully at the site or nearby. Black-crowned Night Herons were reliably present in July, but may well have arrived from another nesting colony.

It’s interesting to look at this cluster of herons at Fresh Pond in a larger geographic context. 

The following maps show sightings from the eBird database of all four species in 2012 (as of mid July) and over the past 10 years or so.  Here’s one species as an example:

Black-crowned Night Heron, 2012 (as of mid July)

Black-crowned Night Heron, all years in eBird (mainly last ten):

Within the mapped area (approximately 10 x 15 miles) and outside the banks of the Charles and Mystic Rivers, Black-crowned Night Herons seem to be concentrated along a long north-south corridor of green, wet spaces, including Black’s Nook.  The corridor extends from the Middlesex Fells through Upper and Lower Mystic Lakes, Arlington, Alewife, Fresh Pond, and Mt. Auburn Cemetery to the Charles River.  (Cont.)

Monday, March 19, 2012

Tree Swallows

The Black’s Nook Project has done its small part in confirming an eBird-NOAA prediction of early Tree Swallow migration this year by reporting six Tree Swallows on 3/18 at Black’s Nook and a pair again on 3/19.  This happens to be three days earlier than the earliest previous first-arrival record for Fresh Pond in the eBird database (out of 70 March checklists from all years). The unusually warm winter in the eastern United States has led to an early movement of birds.

The common understanding of why Tree Swallows return to this region in March is that the benefits of securing early nesting sites outweigh the uncertainties of food supply and weather.  March in New England is usually a pretty stressful time for these mainly insectivorous birds, after all.  But the competition for cavity nesting sites near water is intense, and that limited supply of sites apparently rewards early staking of claims, despite the risks. The birds delay building nests until weeks later, but defend their sites in the meantime (Winkler et al, 2011; Sibley et al, 2001).
At least one swallow repeatedly approached the entrance to the nesting box marked #8 near the golf course, presumably checking it out on Sunday.  Monday morning birds were again observed at the box.

We can’t prove from this evidence alone that the birds wouldn’t have stopped here anyway. But these observations, together with other things we know, suggest the importance for this species of managed spaces like Black’s Nook.  These boxes are maintained by volunteers from the Friends of Fresh Pond Reservation. Elizabeth Wilde of the Friends arranged to have the boxes put up earlier than usual this year, literally the day before the first report, precisely because of the warm temperatures and predictions of early arrivals. A great example of bird data informing management practice.  The boxes are used successfully every year.  Ideally we will confirm nesting later in the season.   

The Friends of Fresh Pond have reports on their nesting box program since 2004.   For more on Tree Swallow life history and conservation see the sources below and PRBO Conservation Science.   And for an example of how eBird data is being used to study the timing of migrations in response to temperature (and climate change) see the eBird story on this just-published paper.

Sunday, February 26, 2012

American Woodcock in February

Having seen a report of an American Woodcock at Fresh Pond on February 21, I stopped by Lusitania Meadow to try my luck at dusk on February 24.  The wooded area adjacent to the field seemed like a good bet for appropriate habitat, and sure enough at 5:50 I heard this repeated "peent" in the woods just off Concord Avenue (click on the triangle to play the sound):

I ran my iPhone voice memo through Cornell's Raven Lite software, and generated this spectrogram fingerprint of the call, which neatly matches the reference below:

Recorded Lusitania Woods, Fresh Pond, Cambridge, February 24, 2012, 5:50 p.m. with iPhone. Spectrogram created in Raven Lite 1.0., ©2003-2009 Cornell Lab of Ornithology.

      Figure 3. Vocalizations of the American Woodcock: (a) Peent preceded by Tuko (Borror Lab of Bioacoustics (BLB 325 Courtesy of the Borror Laboratory of Bioacoustics, Ohio State University.
From: Keppie, D. M. and R. M. Whiting, Jr. 1994. American Woodcock (Scolopax minor), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online:

This is early for woodcocks. Cornell researchers have noticed early migrations in 2012:

 “The exceptionally warm winter across much of the Eastern US means that migrants may be on the move earlier than usual this year, and we are already seeing this in many places… Woodcocks typically move into mid-latitudes starting in late February, with arrival in more northerly states in mid-March. Many places (as far north as Maine!) are already seeing pioneering woodcocks up to three weeks ahead of schedule, and like Killdeer, this pattern can be expected to continue. Watch for them in the evening in areas where old fields mix with younger woodlots. On calm evenings, you may hear them 'peenting' and displaying.” 

Early or not, it's amazing that this secretive forest bird—the only sandpiper relative that lives in the forest in North America—can find this small patch of woods in the city. American Woodcocks have specific habitat requirements—wet soils and early-successional forest with access to clearings for their display flights. This bird picked out Lusitania woods at the edge of a sea of roofs and parking lots.

It’s probably migrating through, and won’t stay.  (There are no eBird records of woodcocks at Fresh Pond in the summer.)  On the other hand, these birds want the exactly kind of habitat that the disturbance history and meadow management practices have created at Lusitania Field.  If there’s woodcock habitat here, this is it. 

In any case, this “peent” sound in February speaks to the importance of conserving patches of forest and meadow habitat in urban settings.