i actually think CBCs and other NAB data, plus maybe EBird, are the best method to capture answers to questions about bird populations. People tend to think "birder" data are noisy and unpredictable because the methods are sloppy - but in fact the main reason for big variability is the nature of the data themselves. In other words, using the best, most precise, "Scientific" methods possible on Bonapartes Gulls, one world still get pretty much the same very large variability seen in these graphs. The "messiness" is factual, and not an artifact of sloppy methods. We learned this from the breeding bird censuses (high precision that failed to remove high variability) and realized that high spatial coverage is much more important than high precision, and therefore came up with Breeding Bird Surveys, which have proven very good at revealing changes in populations. People are wed to the "Normal distribution" which applies well to genetic data and measurements (wing lengths, etc) but is wildly inaccurate for counts of birds (or any other organisms). Doesnt mean there is something wrong with counts; rather, there is something wrong with trying to apply a normal distribution to them. We now have mountains of statistical techniques (negative binomial distribution; many others) that successfully deal with data such as abundance of bonaprates gulls collected by birders. I think there is strong evidence that CBC data accurately reflect population changes, both for statistical reasons and also for their comprehensive geographic coverage.
there have been many instances in the past 30 years where perceived population declines have been challenged on the grounds that "the birds went someplace else". in most of these instances, that has turned out, from later analysis, to be untrue On Wed, Oct 14, 2020 at 7:11 PM <rc...@nyc.rr.com> wrote: > I’m most pleased at the developing discussion on small gulls and other > bird population fluctuations (mainly declines ☹). > > > > One quick thought – on choice of statistics (which several raised): when > dealing with crowd sourced data (yeah, that includes CBC, well-tended > though it is), it’s always apples and oranges to some degree. If the effect > is strong enough, it will carry through across a number of approaches (as > seems to be the case here, not insignificantly!). > > > > The best evidence for this discussion would be either (1) a Zeusian, > universal, longitudinal population census worldwide, or (if Zeus isn’t > around), a really accurate sampling census, based on sightings by a giant > number of random field groups, to determine likelihood. Neither such > precise dataset is readily at hand. So we have to squint at what we have, > augmented by rich, expertized field observations, which fortunately are in > at least adequate supply. > > > > As I said at the start of my post, I didn’t have much time this morning > and grabbed what I could find quickly. Very pleased to see additional info > others have posted (e.g., from CBCs where the data parameters are known > personally, and thus trustable, as w/Dick’s), or longitudinal counts from > Niagara (a world concentration point, with systematic censuses), or even > careful notes from Gravesend Bay (though movements here can be ephemeral – > but hey, it’s still information, and I like the place!). > > > > Hope folks keep grappling with how to best sort all of this stuff out. > Citizen science at its best should actively embrace these issues – even > though I actually kind of hate the term “citizen science” as it’s sort of > condescending and ambiguous, but probably that’s just me. > > > > Best to the list, > > Rick > > > > *From:* Richard Veit <rrvei...@gmail.com> > *Sent:* Wednesday, October 14, 2020 5:07 PM > *To:* rc...@nyc.rr.com > *Cc:* Willie D'Anna <dannapot...@roadrunner.com>; & [NYSBIRDS] < > nysbird...@list.cornell.edu>; Emily Peyton <epey...@nyc.rr.com> > *Subject:* Re: [nysbirds-l] Bonaparte's Gulls > > > > here is a plot of bonaparte's gulls on massachusetts cbcs 1979-2018. All > the major coastal aggregation spots i know of (Campobello Is, maine, > Newburyport, MA, Provincetown and Nantucket, MA, Jones Inlet, NY, Staten > Island, NY) have dropped from thousands to tens of thousands of birds to > handfuls. We missed it on the Staten Island CBC this year and saw hardly > any at Nantucket. I used just total birds rather than birds per party hour > in the graph because the birds are all in one place and are either seen or > not seen, regardless of how many people or groups on the cbc (more or > less)........ > > > > On Wed, Oct 14, 2020 at 10:08 AM <rc...@nyc.rr.com> wrote: > > 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 > > > > -----Original Message----- > From: bounce-125036389-3714...@list.cornell.edu > <bounce-125036389-3714...@list.cornell.edu> On Behalf Of Willie D'Anna > Sent: Wednesday, October 14, 2020 9:34 AM > To: '& [NYSBIRDS]' <nysbird...@list.cornell.edu> > 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/nysbirds-l@cornell.edu/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/ > > -- > > > > > -- > > Richard R. Veit > > Professor, Biology > > CSI/CUNY > > 2800 Victory Boulevard > > Staten Island, NY 10314 > > 718-982-4144 > > fax 718-982-3852 > -- Richard R. Veit Professor, Biology CSI/CUNY 2800 Victory Boulevard Staten Island, NY 10314 718-982-4144 fax 718-982-3852 -- 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/nysbirds-l@cornell.edu/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/ --
