Peregrines & Poison

[The Peregrine Chick]

Egg shell thinning was the reason for the peregrines declines post World War 2 and it was as a result of the DDT and related DDE chemical pesticides.  The DDT killed the bugs it was suppose to kill (and lots of others it was not a good idea to kill) and when those bugs were eaten they built up in the stored fat of the prey bird species which in turn were eaten by birds of prey (such as the peregrines) and again was stored in their fat reserves.  The birds themselves weren't affected but the stores they used to produce the eggs and the eggshells were.  The eggshells were thinner and this caused them to crack and the embryos/chicks would be crushed (peregrines are pretty light so it doesn't take much), the shells would crack and infection etc would get in and the embryo/chick would die.

So you weren't wrong in what you read, there are poisons that cause eggshell thinning, fortunately those particular chemicals have been banned in Canada, the US and Mexico for a few decades.  Further south, were many peregrines overwinter, DDT & DDE-related pesticides are still in common use which is still of concern for peregrine researchers but eggshell thickness seems to not be a problem currently.  What is a problem at the moment seems to be the fire-retardent chemicals that we have sprayed on everything and which is now common in the environment.  There are some concerns about behavioural (rather than the DDT physiological) changes which are disturbing.  Will see if I can't find some more recent information on that and will post it here on this thread.

[The Friesens]

Thank You for the Information. I was a little concerned as I thought I had read on one of the peregrine sites that if the falcons eat tainted(birds) so to speak that the results could be to the effect of thin shells of the eggs making them a more at risk species. Maybe I misunderstood. Thank you again for enlightening me

[The Peregrine Chick]

The City doesn't actually do its own pest control, they contract out.  We keep in touch with the pest management companies in town so they know when the peregrines are home and where they are.  As for the peregrines eating poisoned pigeons, if we have had any (and I'll have to check) we haven't had a poisoned peregrine reported/found in Manitoba in at least 20 years.  Peregrines may eat pigeons, but they don't seem to go after sick birds, in part because sick birds don't fly, they sort of hide because they know they are vulnerable.  In part because an sick bird has the potential to make the peregrines sick and they know that, particularly when they don't lack for opportunities.  The Provincial Government does handle their own pest management but they stopped using poisons on provincial buildings because of the peregrines about a decade ago.

[The Friesens]

Tracey,

I have heard that the city of winnipeg or some building owners have used (poison) or some substance to eliminate the pigeons and other large birds. Do you know how accurate this is and doesn't that effect our falcons through the food chain?