Hi, Jim, all,
Thanks for the reminder to say something about TREe Swallows' getting caught
in nestboxes.
There was a report on bluebird-L this year of about 200 dead TRES being
found in one location in western NY.
There does seem to be a certain amount of inevitable mortality following
TRES migration, especially in the north, but some of it is not so
inevitable.
At Oregon Ridge Park in Cockeysville (Baltimore Co) we used to find 10-15
TRES in the nestboxes each year, most of them dead. When I added "ladders"
to the boxes, the number dropped to zero in most years of trapped TRES not
suffering from a visible injury.
Although no one is quite sure, the explanation that makes the most sense to
me is that TRES, being aerial feeders, have spindly legs, compared to
EAstern BLuebirds, which, being ground feeders, have stout legs (since they
have to land on them all the time when they're hunting). So when a bluebird
is scouting for a nest cavity, he goes in, looks around, and then hops/flaps
up to the hole and goes out. Whereas when a TRES is scouting, he may go
into the cavity and the combination of hop and flap can't get him all the
way back up to the hole (maybe 6", which is a lot), so he needs some
roughening of the surface under the hole in order to be able to make his way
back out. There is no planed lumber in wild nature.
So what you can do is provide something for the TRES's legs to grab onto to
help it get out of the box. The easiest way to do it is to take a nail or
an awl and simply scratch the wood. You can do this without taking the box
apart. If you take the box apart, or while you're building the box even
better, you can put saw kerfs in the wood, or you can take a piece of
hardware cloth (basically big screen material) made of either galvanized
steel or coated steel or vinyl and staple it under the hole.
If you have planed wood nestboxes and they're screw-constructed you can take
it apart and use a saw to make some grooves under the hole inside the box,
or staple a piece of hardware cloth under there. Without taking the box
apart you can use an awl-type tool to roughen the wood surrface.
Some folks use rough cut lumber to make their boxes.
Some nestboxes are made of PVC pipe or PVC fence material -- you have to
glue something under the hole for PVC boxes.
Actually for the first time in my memory, this year we have found one dead
TRES in a nestbox with a ladder. I think this says something about the
severity of the weather we're having this spring. As far as I know the only
plant food TRES can eat is the berries of the bayberry/waxberry plant, which
we don't have much, if any, of around here. If there are no flying insects
(and I think you need 45 degrees F for insects to be able to fly) then
there's nothing for the TRES to eat. They're known for migrating to find
food, even if it means abandoning a nest where eggs are being incubated or
nestlings are being brooded -- if they stay, they'll all die, if they leave,
only the young will die.
I think it's a combination of weakness/exhaustion and ladders. However, the
ladder part is key. As I say, until this year I don't think we've found one
trapped TRES which did not have a visible injury in a box equipped with a
TRES ladder.
Paul Kilduff
----------------------------------
From: James Meyers <>
To:
Sent: Saturday, April 21, 2007 5:31:22 AM
Subject: [MDOSPREY] Cromwell Valley Park HawkWatch
[snip]
On a sad note, six Tree Swallows were found dead in several Bluebird boxes.
Four were
found in one box (3 dead, 1 survived). I'm no expert, but I think these Tree
Swallows roost
in the boxes and some are too exhausted to get out after their long
migration. Maybe one of
our Bluebird trail Monitors could shed some light on this.
[snip]
Jim Meyers
Parkville Md
_________________________________________________________________
MSN is giving away a trip to Vegas to see Elton John. Enter to win today.
http://msnconcertcontest.com?icid-nceltontagline |