I took 20 measurements of the egg using calipers on the broken edges to try and avoid the curve and the average was 0.31 mm (standard deviation of 0.02).
According to USGS Biological and Ecotoxicological Characteristics of Terrestrial Vertebrate Species Residing in Estuaries ‘Peregrine Falcon’ pre DDT shell thickness is generally around 0. 35-36 and post DDT it dropped by 10-22 % to 0.27-0.29.
So our Swift’s eggs would seem to be quite thin. This may reflect the high percentage of starlings and pigeons in their diet as contaminants tend to accumulate particularly strongly in these species.
I’ll see what it costs to have the eggshell (which is now in pieces) tested for contaminants.
Comments are welcome.
Maybe it is just due to Swift’s age that the shells are thin. Hopefully the remaining 2 are a bit thicker! Would be interesting to find out if the shell has contaminants-provided not too costly!
What sort of contaminants would accumulate in starlings and pigeons?
I hope the remaining eggs are thicker as well.
Hoping & praying that the two eggs come to fruition!
Am sure that if you ‘passed the hat’ round some donations from Swift & Beau’s fan club would be forthcoming to help out with testing costs as we are all interested in finding out cause of thin shelled eggs!
Attn; Cilla or Scott,
Are there still a lot of toxic chemical pesticides used in Australia?? We have the most of the “bad ones” (like DDT etc) banned here in Canada & USA but there are many others on the brink of being toxic to raptors. Our Peregrine numbers are rebounding nicely but there is still much work to do.
DDT is still being used in some parts of the world.
And there are new dangers introduced in our environment, such as flame retardants.
Many have hormone-altering properties that could influence the forming of the egg shell.
We now know that plastics are broken up into microscopic grains and already have worked there way up into the food chains.
Recently they were found in German beer.