[texbirds] Rockport Black Skimmers - egg and hatchery farm for gulls
- From: MBB22222@xxxxxxx
- To: texbirds@xxxxxxxxxxxxx
- Date: Sun, 12 Aug 2012 23:25:01 -0400 (EDT)
The ruling pigs declared in George Orwell’s Animal Farm: “ALL ANIMALS ARE
EQUAL, but (they added) some animals are more equal than others.”
I was planning to write a note about tragic situation of Rockport’s
skimmers colony this year for quite a few weeks now. Even promised some people
interested in Rockport’s skimmers to do so but there were quite a few things
happened during last few months which had a huge impact on my lifestyle. As
I cannot go to the field during weekdays as freely as I was able to do for
so many years I am trying to get out of the city on every weekend when I
have time available; much better thing to do than spending too much time in
the front of the computer. Recent article in Caller Times mobilized me to
finish these notes that I was writing for couple months.
Last year I posted here some notes about Laughing Gull ‘specialists’
decimating Black Skimmer colony in Rockport. At that time I contacted a few
people there (who I tough were monitoring skimmers) but from received emails I
learned that nobody was aware of this problem (gull’s predation) as real
there and low reproduction was blamed on other reasons. Local newspaper
asked me (in email) to call them but nobody returned my call; only later I
read
their article that some other people decided to accept gulls’ problem.
Last year I collected a lot of interesting data about skimmers’ nesting sites
(not only in Rockport) so I was interested to do some data comparison. I
tried to find out if I can get access to check some numbers (number of nesting
pairs, fledged chicks etc) from recent years from the Rockport’s colony
(both LAGU and BLSK). I did not have luck with that so to not keep wasting my
time I decided just to put my data ‘on file’. Normally I would not feel
bad about it, as I learned long time ago that one should count only on
himself, but the tragic situation and future (perhaps better said: no future)
of
this colony made me make those calls I wouldn’t do if this was just a
curiosity case. Rockport is too far for me to visit on regular basis. This
year
I did not plan to visit this colony as my travel schedule was already too
full but as I had opportunity to be there during the Memorial weekend so I
jumped on it. I also found an earlier report from this year on the net
describing plans to relocate the skimmers’ colony by using speakers, decoys,
placing drench material in new location, etc. Maybe the curiosity kills cats
but I thought it would be interesting to see what is happening there.
Without going into too much details (not a purpose of this post) even basic
thing as location of new place for nesting seems to call for disaster – it is
located in middle of the LAGU nesting area – just like being surrounded by
enemies all the time! Anyway skimmers seemed to have more common sense and I
did not see any on this new prepared site near the decoys. All skimmers
voted for no changes – so impact of decoys, calls from speakers and new
substrate had no effect. It seems that despite good intentions some groups try
to apply ‘trial and error’ approach when trying to solve problems rather
than to try doing a research first in less endangered colonies to learn more
about behavior and nesting site optimum requirements. As I said this is not
issue to discuss in my post today anyway as it will become simply way too
long. I decided to revisit colony a few more times during weekends as what
I found there during the first visit was tragic. So was situation during
next visits. Plain and simple I personally do not see any future for this
skimmer colony without removing nesting LAGU from this area first and then
deal with other problems.
Now, why I call skimmers’ colony an egg and hatchery farm for gulls. Well
because this is exactly a case there. From thousands of nesting LAGU quite
a few more than last year decided to become specialists and supplement
their diet by regularly collecting skimmer eggs and fresh hatched chicks. They
patrolled and controlled air zone above skimmers’ colony most of the time.
It is almost unbelievable how passive most skimmers became there. But then ‘
nec Hercules contra plures’. In fact there are probably more incidents of
LAGU defending their feeding territory (right near skimmer’s nests) than
skimmers trying to defend themselves from gulls. When compared to last year,
LAGU evolving behavioral changes are impressive as are their new developed,
very efficient skills to collect eggs and chicks from under
incubating/brooding skimmers. There must be a reason why gulls are thought to
be very
smart. Again, it would take too much time to write about this and I am not
sure that more than few would have an interest to read about it in detail.
So lets jump straight to facts. I spent many hours watching skimmers’
colony on each day I was there. Because I spent only part of each day to
observe just activities inside the colony I could only roughly estimate the
losses. Also I could not observe the whole colony at any given time as I was
often concentrating on single birds and documenting their behavior so there is
no telling how many ‘kills’ I missed to register. To show an extreme
example I have seen loss of 3-4 eggs/chicks in some single hours. Of course
predation rate per hour was usually much lower but there was no way skimmers
could keep production that high anyway. So, what I am trying to say without
spending days from sunrise to sundown (well once I saw LAGU taking skimmer
chick about 15 minutes after sundown so watching colony at before sunrise
and after sundown could improve results) and watching carefully the whole
colony one can end up with wrong answers – averages either too high or too
low.
To make some speculation I will assume that on average at least total of
10 eggs and chicks were taken by LAGU (very low estimate) every day when
eggs were lay and colony had new hatched chicks.
Now let’s assume that we will have 100 pairs of skimmers trying to
reproduce (on one day I counted over 300 adults on and near nesting grounds).
Then
let’s assume that during nesting and renesting (after keeping to loose
eggs/chicks to LAGU predation) they will produce perhaps average of about 6-8
eggs (just speculative number) before they either give up laying or be lucky
to keep 1-2 chicks alive (chicks about one week old and older are safe,
from LAGU predation, when no other factors occurs). Let’s say skimmers will
lay eggs during couple months and produce 600-800 eggs/hatched chicks
(toward the end of nesting season production will slow down, some chicks, I
hope,
will survive but the average because of low estimate might be even higher
than 10 successful predations per day). LAGUs will destroy most of it. No
wonder that this colony is lucky if 20-30 chicks are fledged per year (had
seen about two dozen fledglings this year). Remember that there are going to
be some losses no matter what due to other reasons. Also it will take a
huge effort to produce a lot of eggs and spend a lot of time
incubating/brooding to have just a few chick fledged per season. So these are
the reasons
to call this place a farm. Healthy skimmer colony of this size with no
predation (and no disturbance) could/should produce at least 100-150
fledglings
in year with no floods and plenty of food. If we had some catastrophic
weather this summer these few chicks that survived gulls attacks would be most
likely wiped out and probably none would stay alive to take the first
flight.
During my early visits I usually only saw several skimmers chicks and very
few were more than few days old. I do not know when skimmers started to
lay eggs so cannot tell if there are not older chicks because of gull
predation or I just visited the place when first chicks just started to hatch.
There are a few interesting consequences of gull predation, or they seem
to be related to this problem.
I have never seen so much action like this before with so many copulating
skimmer pairs every day – place often looked like Caligula’s palace; but I
guess they had to keep egg production to feed hungry gulls. In one case
after ending with empty scrape one pair was copulating about an hour later
after the lost.
With loosing so many eggs and chicks some pairs were ending with empty
scrapes and they tried to relocate the scrape spot and trigger many extra
conflicts with neighbors. Many gravid females were flying around and looking
for a new place to lay egg. And just an extra note; skimmers can be vicious,
and believe or not, females are often more vicious than males so finding a
place to nest can be a challenge. BTW I have seen 3 females fighting each
other over one male who was ignoring all three of them (and even chase away
the winner). Lucky guy, well, perhaps not.
Well, I will post just a few photos to illustrate the problem; some might
be too graphic for sensitive people so make your own decision if you want
to see those.
Very often one could watch gulls landing and standing close to skimmer’s
nests and chasing other gulls that tried to land there; same fighting in
air-zone above the colony. Also something I have never seen anywhere else (at
least not yet) - LAGUs at the best could be chased away in midair by
skimmers but when chases stop they were following skimmers back to the colony
right behind their tails. In many cases (something I thought is unthinkable)
LAGUs were not flying away but faced the attacking skimmer and fought back,
even worse they often chased skimmers around. This also I have never seen
before – desperate skimmer that could not scare away LAGU from the middle of
colony decided to defecate on it, BTW missed it (will include the photos)
I want to finish this ‘report’ with at least one good note. This year
there was practically no human disturbance and a few small incidents did not
cost any egg/chick lost. Couple of times people with PS or short lens
cameras tried to get too close to the fence; there was a few broken wing
displays
as response but a few other skimmers took care about intruders by diving
at or flying close around them. One time somebody’s swimming tube rolled
all across nesting site but this triggered only a small panic and,
thankfully, there were no gulls above at that time to take an advantage of
situation.
I also met couple of very nice local photographers who shared a lot of
interesting information about the Rockport and surrounding locations.
So below are just few photos to illustrate some problems, I had no time to
process so many taken photos. BTW aerial disputes were incredible this
year but I did not even process yet those I took a year ago.
Examples of LAGU taking skimmer chicks:
_http://www.pbase.com/mbb/image/145347245_
(http://www.pbase.com/mbb/image/145347245)
_http://www.pbase.com/image/145347376_
(http://www.pbase.com/image/145347376)
And eggs:
_http://www.pbase.com/mbb/image/145347364_
(http://www.pbase.com/mbb/image/145347364)
_http://www.pbase.com/image/145347366_
(http://www.pbase.com/image/145347366)
LAGUs fighting for exclusive rights to farm inside nesting colony right in
front of watching skimmers:
http://www.pbase.com/mbb/laughing_gull_territorial_fights_inside_black_skimm
er_nesting_co
LAGU confronting BLSK in midair:
_http://www.pbase.com/image/145347252_
(http://www.pbase.com/image/145347252)
Additional problem – LAGUs stealing fish from skimmers preventing chicks
from getting food:
In midair:
_http://www.pbase.com/image/145354082_
(http://www.pbase.com/image/145354082)
On ground, literally knocking down skimmer adults trying to feed young:
_http://www.pbase.com/image/145354103_
(http://www.pbase.com/image/145354103)
_http://www.pbase.com/image/145347420_
(http://www.pbase.com/image/145347420)
Gravid BLSK female looking for spot to nest
_http://www.pbase.com/image/145347381_
(http://www.pbase.com/image/145347381)
Well, many more photos can be found in folders here:
_http://www.pbase.com/mbb/from_the_field_
(http://www.pbase.com/mbb/from_the_field)
including examples of LAGUs killing weak older chicks during bad weather;
just scroll down.
Mark B Bartosik
Houston, Texas
Other related posts:
