Hi all,
I don't want to downplay some of the "big-issue" concerns that have been touched upon in this thread, my guess is that these swallow mortality events this spring are not as nefarious. Without examining the birds, my guess would be that these birds have starved to death (a close examination would reveal how much fat these birds have or don't have).
Without the time for a treatise on the topic, I would say that it fits a pattern of mortality for aerial insectivores that unfortunately occurs in cool to cold springs. Simply put, flying insects have not been out in abundance statewide, they are appearing late, and often in lower quantities than we - and our birds - are used to. While that's great for our comfort from biting insects, its not good if your life depends on insects in the air.
We've received numerous reports of Tree Swallow mortality and nest abandonment in boxes this spring, and a slow start (or worse) for bluebirds. I expect Purple Martins and Chimney Swifts were particularly hard hit by the cool weather that not only delayed many insect hatchings, but also suppressed abundance higher in the air column where these birds feed.
Occum's Razor suggests that these Barn Swallow deaths are the result of starvation, as we have definitely had the weather this spring that is a challenge for aerial insectivores. Although technical, this article is a leading reference on the concept of "fat scoring" on birds:
For something more user-friendly, type "Fat scoring on banded birds" into Google Images and you'll see some pictures of birds' fat reserves (it is what allows them to migrate and survive lean periods). At the very least, I would start with this idea, and if it proves to be incorrect (e.g. the dead birds all have lots of fat), then we would look into other issues such as disease, poisoning, etc.
-Derek
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Derek and Jeannette Lovitch
Freeport Wild Bird Supply
541 Route One, Suite 10
Freeport, ME 04032
207-865-6000
www.freeportwildbirdsupply.com
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Derek and Jeannette Lovitch
Freeport Wild Bird Supply
541 Route One, Suite 10
Freeport, ME 04032
207-865-6000
www.freeportwildbirdsupply.com
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From: Richard Harris Podolsky <richardpodolsky@gmail.com>
To: "maine-birds@googlegroups.com" <maine-birds@googlegroups.com>
Sent: Monday, June 8, 2015 10:06 PM
Subject: Re: [Maine-birds] Dead Barn Swallows
This isn't normal and is troubling. Barn swallows are long-lived birds that ought not be dying en mass. Birds are sentinel organisms and we need to listen to them. A mortality event like this is a real concern. You are likely only finding the tip of the iceberg. Odd for them to survive the winter and migration only to die at their nest site. It is time to reach out to a local agriculture extension, avian haven, and a qualified veterinarian.Did they build their nests as usual? Two possibilities are their insect food source and the mud they use for nesting as a source of toxins and/or disease which I suspect is at the root.--Swallows including martins have been in decline in the the northeast and Maritime provinces for some years now.Here is an article to read and perhaps contact the folks mentioned:I will continue to look into this matter. Others in the group ought to share their perspectives on swallows too.Best - Richard
On Monday, June 8, 2015, Richard Harris Podolsky <richardpodolsky@gmail.com> wrote:A few things to look for -
•has the flight path they take into and out of the barn changed in any way? Specifically, are their any obstacles? Collision deaths can cause broken beaks or necks or wing breaks in otherwise plump and healthy birds. Look for that.
•have you observed normal foraging flight behavior? It has been cold and it's possible their aren't enough insects.
•do you or your neighbors use any pesticides?
•I suggest freezing the dead birds you find in a ziplock. I have heard of diseases in swallows before and last May I found dozens of barnys dead on the Dry Tortugas from what appeared to be disease given the number of stricken birds.
•finally contact Avian Haven or a vet who knows about song birds.
It is sad and upsetting to see long-lived birds die prematurely.
Please report back if you learn more.
Richard
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