After speaking this morning with Mike Cooper about our recent impressions of Lesser Black-backed Gulls on Long Island, I thought it might be best to expand the conversation.
The basic question that Mike raised (I think I'm re-stating it correctly) is whether recent reports of large numbers of LBBGs along the south shore of western LI represent southbound migrants or birds continuing from summer aggregations. My impression is that both factors are contributing to the pool of birds present recently, and that this combination itself might be somewhat unusual. In recent years, increasingly large numbers of immature LBBGs have summered on LI, often in fairly discrete aggregations around various ocean inlets, with Jones Inlet consistently hosting the largest counts. Even so, it can be difficult to find the birds involved in these flocks from day to day and week to week throughout the summer, probably because they generally forage far offshore (note the consistent over-representation of this species among large gulls on pelagics, as vividly illustrated by Sean Sime's account of the 31 Aug trip to Hudson Canyon), and because few people work methodically and consistently at trying to find and count them. In the past, these loafing flocks seem to have broken up (perhaps moving south) just ahead of the arrival of migrant adult LBBGs from the far north, in early to mid September, and well ahead of the arrival of juveniles in late September to early October. The largest count on LI this summer that I am aware of was 33, counted by Pat Lindsay, Billy Hanley, and me at Jones Beach West End, on 4 Sep, during a favorable confluence of hide tide and strong east winds. This aggregation consisted of 16 second calendar-year (SY), 12 third calendar-year (TY), and 5 fourth calendar-year (4Y)--with the acknowledged possibility of some mis-assignment between SY and TY, and between TY and 4Y. It surely overlapped in content the count from a month earlier at the same site of 26 immatures of various ages by Shawn and Mary Beth Billerman. The complete absence of full adults on 4 Sep makes me question whether southbound migrants were involved at all, but it is of course possible that young birds summering to our north, for instance on Nantucket, might be sliding down the coast and mixing with our summering birds. Jane Ross and Magda Binion saw the first full adult I am aware of this fall at Sagaponack on 5 Sep, a rather typical arrival date for this age class. My group missed that bird, but we did see an SY bird and SY/TY bird at Sagg on 5 Sep. Later that day, Pete Morris, Taylor Sturm and I saw an exceptionally early fresh juvenile at Montauk Pt (1 Oct is a more typical arrival date). Pat Lindsay and I saw our first full adult of the fall at Cupsogue on 7 Sep; indicative of the complexity of the situation, a TY type was present with it. The recent, expected, arrival of full adults, as well as the less expected, extremely early, arrival of a juvenile, prove that migration has commenced. What we don't understand at present is the timing of movement of the SY and TY birds that have become so prevalent during summer along the mid-Atlantic coast. Specific questions I would pose to this highly informed forum are the following: 1. My records indicate a very abrupt arrival of full adults starting around 5 Sep, with almost no convincing earlier exceptions. Are others aware of such exceptions? 2. Similarly, juveniles normally appear to arrive after about 23 Sep; the Montauk juvenile of 5 Sep 15 is an outlier, but perhaps others are aware of other convincing early records. Are these outliers perhaps attributable to predicted but as yet undiscovered North American breeders? 3. Really large counts of SY and TY birds (>20) seem to be restricted to the summer months, sometimes persisting into early September (as on 4 Sep 15), but later on, I've encountered these younger immatures only in markedly smaller numbers (single digits). After late October, these non-juv immatures appear to be actually rare on LI. Does anyone have data or a strong impression about the timing of movements of these one and two year-old birds? Shai Mitra Bay Shore ________________________________ CSI Tops MONEY magazine’s Best Colleges list for 2015-2016><http://csitoday.com/2015/07/csi-tops-money-magazines-best-colleges-list-for-2015-2016/> -- NYSbirds-L List Info: http://www.NortheastBirding.com/NYSbirdsWELCOME http://www.NortheastBirding.com/NYSbirdsRULES http://www.NortheastBirding.com/NYSbirdsSubscribeConfigurationLeave.htm ARCHIVES: 1) http://www.mail-archive.com/[email protected]/maillist.html 2) http://www.surfbirds.com/birdingmail/Group/NYSBirds-L 3) http://birdingonthe.net/mailinglists/NYSB.html Please submit your observations to eBird: http://ebird.org/content/ebird/ --
