Date: 7/5/18 9:14 am From: David Sarkozi <david...> Subject: [texbirds] Re: Eurasian collared dove population crash?
I would also caution the use of anecdotal memory as a baseline for comparison, we don't tend to remember negative observations as much as positive in my experience. As an example I was compiling the sighting board checklist for Anahuac NWR. I used the 100 most reported birds from eBird by highest percentage of reports by month, i,e, I used the month with the highest percentage of reports to rank the top 100. American Bittern did not make the cut, it's highest month was only 25%. I had a fellow volunteer differ with my analysis saying her sa the bird almost every visit in season. I asked him to count the number of visits in a row he saw the bird to prove me wrong. After 4 negative visits he conceded the point.
Our memories of how often we see a bird are often very flawed, unless we are counting we don't recall the negatives very well, just the positives.
On Wed, Jul 4, 2018 at 8:59 AM, Joseph Kennedy <josephkennedy36...> wrote:
> A couple of years ago I sort of noticed that there were not as many > collared doves around the smith point area. Did not see them crossing the > bay and places that had large numbers had fewer. Last summer there were > fewer but Harvey had something to do with it but did start checking other > spots. Numbers on Bolivar were down too as well as around the house. > > This summer actually went and censused. > > A few years ago I could see 10-15 male doves do their courtship flight > over voss and westheimer when I stopped at the red light. This year I see > none. The several pairs at the grocery store are gone except for one pair > and none have come by the feeder. > > Numbers are down maybe 90% on bolivar based on general impressions rather > than ticked off numbers. > > Had trouble finding more than single pairs at smith point Monday with none > at some points that used to have lots > > This population drop has occurred over 3 summers in places where I go and > sort of count birds every week or at least very often year round. So it is > not just a local event. > > Has anyone noted similar trends elsewhere. Similar population drops have > affected other invasive species after an initial great spurt in numbers as > predators and parasites bring the newcomer into control. > > The changes at home have not affected the mourning dove and white-winged > dove numbers; if anything they are both up. Rock pigeons numbers are up > significantly on Bolivar in the same places that I noted collared dove > population decreases. And those two species do not compete for nesting > sites but perhaps for food. > > -- > Joseph C. Kennedy > on Buffalo Bayou in West Houston > <Josephkennedy36...> >
-- David Sarkozi Houston, TX (713) 412-4409 twitter ID dsarkozi