Greenlandic Peregrines will have normal eggshell thickness by mid 2030’ies

• Main Authors: Falk, Knud, Møller, Søren, Riget, Frank Farsø, Sørensen, Peter Borgen, Vorkamp, Katrin
• Format: Conference Object
• Language: English
• Published: 2017
• Subjects: Vandrefalk; Grønland; Peregrine Falcon; DDT; DDE; eggshell thickness; Greenland; Arctic; Canada; Falco peregrinus; greenlandic; peregrine falcon; vandrefalk; Alaska; Pandion haliaetus
• Online Access: https://forskning.ruc.dk/da/publications/8e4fb586-b7a6-4f40-8ec2-5353cff27688; https://hdl.handle.net/1800/8e4fb586-b7a6-4f40-8ec2-5353cff27688; http://www.peregrinus.pl/files/peregrine_conference_2017/4th_peregrine_Conference_Abstact_book_web.pdf

Since it was first shown that DDT caused eggshell thinning and breeding failure in wild peregrine falcon (Falco peregrinus) populations, the effects on the eggshell thickness and breeding success in high-trophic level birds have been widely documented. Studies of peregrines and ospreys (Pandion haliaetus) in Europe have documented that it took 30 years from DDT was phased out until eggshell thickness was back to normal pre-DDT levels. In Greenland, the peregrine population has been the subject of long-term studies, and a previous study of eggshell thinning found a significant increase over time (1972-2003) in thickness of eggshell fragments from West and South Greenland. As part of ongoing updates of a previous comprehensive analysis of persistent organic pollutants in peregrine eggs from South Greenland, now covering 1986-2014, we extended the time series for eggshell measurements and reinterpreted data for a 43 year time span. Mean shell thickness was estimated for 184 clutches based on fragments from hatched eggs, and for 56 whole addled eggs from 44 clutches. During the period 1972-2014 there was a highly significant increasing trend in the average eggshell thickness of 0.25% per year. This corresponds to a change in eggshell thinning from 13.9% to 3.4% in 2014 when compared to pre-DDT eggs collected in Greenland. With the current rate of change, a “normal”, pre-DDT shell thickness is predicted to be reached around year 2034. However, a few clutches are still below the critical limit. The slower recovery of the shell thickness in the Greenland population as compared to other studies is likely indicative of the slower phasing out of DDT in the Greenlandic peregrine’s wintering grounds in Latin America. The shell thinning in the Greenlandic population crossed the 17% “danger limit” associated with population declines probably only for a few years, if ever, contrary to the populations of the same subspecies in Arctic Canada and Alaska. The long-term sampling of eggshell fragments allowed us to verify that the ...