This discussion has been very interesting. I've enjoyed comparing the perceptions and experiences of many friends around the region. Having birded the coastal Northeast for over 40 years, I've witnessed several kinds of changes in the status of Bonaparte's Gull in my "expanded patch" of coastal Long Island and Rhode Island. Willie's points about different modes of occurrence (early fall migrants, late fall migrants, over-wintering birds, spring migrants, over-summering non-breeders) deserves careful attention, as does Shane's observation that large counts of this species vary greatly not only from year to year, but also from day to day within a season. The complexity of this species' modes of occurrence and its extreme variability from site to site and from year to year make it difficult to draw firm conclusions about its overall status. Ironically, these challenges have given us a bit of a refuge from our worst fears as we've watched the diminishing numbers--"maybe they're just doing something different, somewhere else."
In my own areas of concentrated field work, little doubt remains that, at a minimum, really large counts have been much less frequent for many years now, and the species has been missed in recent years on various CBCs where this would have been unthinkable in the past (though it is true that there have "always" been scattered "bad years" when Bonies were uncommon on all the counts). Drawing on Rick's lead, I compiled 50 years of data from four CBCs with which I've been deeply involved for many years: Southern Nassau County, Captree, Montauk, and South Kingstown (RI). These offer a fair east-west transect of the Atlantic Ocean shore of southern New England (to which LI is hereby ceded, operationally). All of these CBCs have had historical totals over 1,000, many years with totals in the 300-800 range, and astonishing dips in recent years. The data illustrate the inter-annual volatility of numbers very well, but also the absence of big spikes for about 20 years and extreme scarcity over the past five consecutive years. In a slightly contrasting approach to Rick's, I think raw counts are more informative than effort-adjusted detection rates for this species. On these four counts at least, the large numbers (when present) are tallied via dedicated effort to particular sites, rather than accumulated as sums of small counts. Note also that the big spike at Montauk in the late 80s was actually over 21,000--I cut it off at 6,000 so as not to reduce the scale for the other data: https://flic.kr/p/2jUWHDm Shai Mitra Bay Shore ________________________________________ From: [email protected] [[email protected]] on behalf of [email protected] [[email protected]] Sent: Wednesday, October 14, 2020 10:07 AM To: 'Willie D'Anna'; NYSBIRDS-L Cc: 'Emily Peyton'; 'Richard Veit' Subject: RE: [nysbirds-l] Bonaparte's Gulls Willie, that is very interesting. I had a quick look at CBC results - for NJ rather than NY, so as to avoid including any "Niagara Falls concentration effect," and the recent trend does appear to be a decline (with a few ‘exception’ years mixed in). In this graph "120" is 2019, and numbers extend back to turn of century. I know "birds per party hour" is a rough measure (I was a CBC compiler for > 25 years, potential party-hour reporting vagaries acknowledged), but the numbers do suggest either a decline in population or a shift in wintering behavior. Sorry, this was a quick take, now back to the ol’ day job… Rick [cid:[email protected]] -----Original Message----- From: [email protected] <[email protected]> On Behalf Of Willie D'Anna Sent: Wednesday, October 14, 2020 9:34 AM To: '& [NYSBIRDS]' <[email protected]> Subject: RE:[nysbirds-l] Bonaparte's Gulls I have enjoyed the recent posts about Bonaparte's Gulls. Some of the highest concentrations of Bonaparte's Gulls in the world occur along the Niagara River, with estimates of 50,000 to 100,000 on some days. It is a spectacle to witness this blizzard of gulls on the Niagara but it seems that numbers have declined, particularly in the last ten to 20 years. It is unfortunate that the only evidence that I can offer for this are my own subjective observations. Counts of gulls on the Niagara have been done sporadically and it is only in recent years that organized counts have been conducted on a yearly basis, with three counts per season (late fall/winter), by the Canadian Wildlife Service. Numbers of Bonies, as they are affectionately called here, month to month along the Niagara, are highly interesting. Twenty to fifty years ago, numbers would begin to build on the Niagara in late July with most of these birds consisting of one-year-olds. By mid August, there would be a significant influx of adults, only just finished with their breeding activities in Canada. Hundreds of individuals could be seen at the source of the river (Buffalo/Fort Erie) and below the falls or in the Lewiston/Queenston area. At times there would be well over a thousand, particularly when there was a good southwesterly blow that would push more of them to the eastern end of Lake Erie. These numbers more or less continued, perhaps with a slight decrease, into October, although whenever there was a southwesterly blow numbers would spike considerably. The big numbers would arrive in late October/early November and reach their highest levels later in November. Numbers would then slowly decrease into January when at some point, ice formation would cause most of them to depart. During some milder winters, several hundred would remain through the season. In a typical winter, only a handful would remain. Starting in February, numbers would slowly start to increase and by late March they would be abundant again. Numbers would dwindle during April and they would be completely gone by about the third week of May, save for a variable number of non-breeding birds. June and July have been the nadir of the Bonies occurrence on the Niagara, although there were usually some immatures around, particularly on Lake Erie. To me, the most dramatic change with the Bonies here has been the numbers during spring. Whereas their spring numbers used to be very comparable to those during late fall, there have been some springs recently where peak numbers were barely into the hundreds, as opposed to the multi-thousands we were accustomed to. August through October numbers are also much lower these days, with counts of over 100 usually only occurring now when there is a bog blow off of Lake Erie. Peak numbers now seem to occur later than in the past, in December rather than November. One change that birders have enjoyed is that numbers of wintering birds are seen more consistently now, likely due to our warming climate. The Bonies are one reason that the Niagara River has been designated an important bird area (IBA). It is obvious that the Niagara River has played an important part in the life cycle of a significant proportion of the species numbers since the 1960s. Whether or not that will continue remains to be seen. Good birding! Willie -- NYSbirds-L List Info: http://www.NortheastBirding.com/NYSbirdsWELCOME.htm http://www.NortheastBirding.com/NYSbirdsRULES.htm 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://birding.aba.org/maillist/NY01 Please submit your observations to eBird: http://ebird.org/content/ebird/ --
