Date: 11/12/17 4:02 am
From: Dom <dom...>
Subject: Re: [JERSEYBI] Corn Crake population increase
Hi Fred,
I wasn’t suggesting the LI bird isn’t a natural vagrant. It almost
certainly is.

And it's true, Corncrakes have registered increases in around 15 of the
last 20 years. But these are increases from a very low base and there has
been little commensurate range expansion. (and by expansion I mean
repopulating areas where it has been extirpated rather than isolated
dispersal. Despite its migratory lifestyle it's a species with high natal
site fidelity).

I can't speak much to the Eastern population, but I know from friends
involved in the Scottish census that it’s a hard bird to survey and the
numbers represent natural breeding volatility more than sustained
improvement or immigration from the east. The 2007 peak is a while ago. For
the last 3 years in the U.K we have seen consecutive declines and we are
back down to 866 calling males this year. I think there were a lot of
questions asked about the 2016 paper that put out the +10,000 birds number.
And of course the IUCN listing is heavily swayed by the Russian population.

Anyway. Let’s hope you’re right that we are witnessing fast adaptation to
changing farming methods! It's an interesting idea and there is some
evidence of this working with Black-tailed Godwit.

Maybe it will with Corncrake too.

Fingers crossed
Dom


On Sat, 11 Nov 2017 at 22:56, Fred Vir <avtrader...> wrote:

> Hello All:
>
> "Corncrakes are suffering huge declines in most of western EU"
>
> Perhaps more than a verb tense issue (are declining vs. were declining) it
> would be pertinent if we actually disagree on absolute population numbers
> and trends after looking at the data. Related we should agree to the actual
> pertinent area of Europe to nearctic vagrancy of the Corn Crake.
>
> The declines were suffered in almost all European pops many decades ago up
> until the 1990s and data shows the drops are now negligible in many areas
> with some remaining populations seeing strong increases. There has been a
> collapse of collective farming methods in E. Europe; pop increases of
> hundreds of thousands of birds there has caused dispersal of birds to some
> parts of W and NW Europe but not all. Recent telemetry shows males
> dispersing for second brood attempts up to an amazing 1,500 Km in one
> season. The pop trend is up nicely in the last 25 years especially if we
> ditch the Western Europe moniker and more accurately agree that the Iberian
> Peninsula is less important a potential nearctic vagrant source than
> Scandinavia.
>
> The source area would then be UK, Ireland, France, Norway, Sweden and
> Finland = "NW Europe".
>
> The pop in the UK recently increased from 480 calling males in 1993 to
> 1,245 in 2007. In Ireland there have been double digit percent increases
> recently. Their numbers increased from 100 birds to 230 in a few years.
> Norway 1995 ~ 65 birds to 160 in 2007. In Sweden 1993 1,000 birds to est
> average of 600 birds in 2009. In Finland the increase was 500% from 1990
> to 2008. There could now be over 14,000 birds there up from ~2,800 25
> years ago. In 1998 in France, on IBAs only, there were 1200 males in 1998
> with the population seeming about the same now.
>
> year ~ 1993 or later ~ 2010
>
> UK 960 2490
> Irel 100 230
> Nor 65 160
> Swe 1000 600
> Finl 2800 14000
>
>
> total 4925 17480 350% increase in the
> source area I propose
>
> Two recent Mid-Atlantic US records in the last ~ 22 months (NY, PA) after
> basically a gap of several decades gives some hope and a possible corollary
> to increasing NW Europe pops. Yes its a small data set but still perhaps
> statistically significant. And if two birds were found there were likely
> more in the last 24 months in the USA.
>
> Admittedly changing/stronger weather patterns can be causal and/or
> additive.
>
> Conservationists have advised European farmers of optimal "crake friendly
> cutting dates" and have had some success in getting farmers to cut from the
> middle of a field out, killing less birds. The crake can have up to three
> clutches and has tremendous breeding capacity with a little help. That help
> arrived several years ago with the results translating to 12,500 more birds
> in NW Europe now than ~ 25 years ago. This is a 350% population increase.
>
> Deforestation in Africa is said to favor wintering crakes so the opinion
> is there are negligible wintering ground issues.
>
> Globally the species has also been found to be more numerous than thought
> or increasing in parts of Western Europe, Eastern Europe, Russia and W
> China. The species has recently changed from Near Threatened to Least
> Concern status (IUCN).
>
> tks
> Fred Virrazzi
> Sec NJ
>
>
> On 11/11/2017 7:52 AM, Dom
>
> Corncrakes are suffering huge declines in most of western EU. I have yet
> to find one in my home country despite them breeding here.
> I also suspect as afro-palearctic migrants they would probably exhibit
> higher nearctic vagrancy if the population was stable. Historic US records
> suggest this too.
>
>
>
> On 11 November 2017 at 12:11, Fred Vir <avtrader...> wrote:
>
>> Several questions/comments were received about the crake.
>>
>> I was also thinking about two of the questions.
>>
>> "When did the bird die?"
>>
>> It seemed to have died at least several hours before before we found the
>> bird. Rigor seemed to have already been passed when the bird was found. The
>> birds plumage and eyes were looking old and matted. And many birders were
>> there for awhile before sunrise on the subject day and should have seen the
>> collision.
>>
>> "As someone who's been watching birds and clearly studying them at
>> length...... do you believe that this bird was indeed a European vagrant,
>> and not an escape from a domestic game farm? " The question went on with
>> good points arguing that this crake was not as timid as the literature and
>> observers say.
>>
>> I don't think this species has been domesticated. Regardless I have seen
>> scores of wintering crakes/rails of various species in 4 continents and
>> even nocturnal species make diurnal appearances (Corn Crakes are diurnal).
>> Diurnal crake spp in SA and Africa can be seen almost daily, at will, in
>> many areas especially in winter as they dart in and out of cover.
>>
>> Some Corn Crakes have recently been observed entering houses via open
>> windows to feed and feeding out of farm pet bowls.
>>
>> This was an underweight individual; certainly hormonal signals that
>> synchronize migratory phenology cause animals to feed aggressively when
>> reserves are physiologically detected as being low. The bird was ~ 20 to
>> 50% underweight. In animals an urgent, innate need for food will often
>> incrementally result in reduced wariness. Remember this bird saw the ocean
>> and may have innately been forced to make a stand to feed at that location
>> or go N----terrestrial predators and cars be damned.
>>
>> Observers of this crake, including me noted that it was both wary of
>> quick movements by people and larger vehicles. Additionally with prior
>> points the strip of bluestem grass may have had more accessible insects
>> that the shrubs; the bird was demonstrating optimal feeding strategies.
>>
>> Also this bird showed up right on time for a putative, natural vagrant.
>>
>> Just when you are about to agree that the bird showed reduced wariness
>> for the above reasons I can slightly switch to your side but disagree with
>> causality (domestication caused the change in behavior rather than rapid
>> microevolution).
>>
>> Going out of the box-------there may have been a recent, rapid change in
>> the genome of this species that makes it slightly less wary. Its
>> pre-agricultural/mechanized agricultural behavior was to move deeper into
>> fields when danger/noise was detected. Its wariness was a partial cause of
>> its industrial age decline. Circling combines starting at the perimeter of
>> a field would mass the birds in an ever smaller central, circle of grass.
>> This led to great mortality via poised shooters or the combines....except
>> for which birds?----- The birds that flushed into more open areas out of
>> the high grass.
>>
>> If you are right about it being a bit less wary than old literature
>> .....could we be observing microevolution?
>>
>> tks
>>
>> Fred Virrazzi
>> Sec NJ
>>
>>
>> How to report NJ bird sightings: see <www.njbrc.com/index.php/
>> reporting-rare-birds/>
>> or e-mail to <njbrcreport...>
>> List help: <jerseybi-request...>
>> List archives: https://lists.princeton.edu/cgi-bin/wa?A0=jerseybi
>>
>
>
>


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