Falcon Research in Greenland, 1973

Abstract

... During the summer of 1972 a research team initiated the first in-depth study of the peregrine falcon (Falco peregrinus) in West Greenland. Eight eyries (nests) of this endangered species were located in an inland sample area of 700 sq. mi. Detailed observations were taken of peregrine breeding behaviour at one eyrie. Seven of the eyries produced young, containing an average of 2.57 young per successful eyrie. This high reproductive rate indicates a healthy population, but analyses of 2 addled eggs revealed high p,p'-DDE as well as polychlorinated biphenyl (PCB) residues and eggshell fragments from 9 eggs showed a 14 per cent decrease in thickness compared with 42 eggs collected in Greenland before the introduction of DDT into the environment. ... The [1973] survey area consisted of 900 sq. mi. (2,330 sq. km.), including ice-cap, lakes, fjords, and other unsuitable habitat totalling about 150 sq. mi. (388 sq. km.). We found 10 occupied peregrine falcon nesting cliffs in the survey area in 1973. ... 9 eyries produced young. Of these 9, 7 were also successful in 1972, while another was occupied throughout the season by an aggressive pair, and at the ninth a lone female mildly defended the cliff. Of the 9 producing eyries in 1973, 1 contained 4 young, 5 contained 3 young each, 2 had 2 young each, and 1 held 1 young. This gives a total of 24 young peregrines and a production rate of 2.4 young per occupied eyrie, or 2.67 young per successful eyrie. These young were counted at advanced ages varying from 2.5 weeks to just before fledging. It is believed that all or almost all fledged. We found 1 occupied eyrie per 90 sq. mi. (233 sq. km.), or 1 successful eyrie per 100 sq. mi. (260 sq. km.). All young were banded with a metal band on the left tarsus and a red plastic band on the right. ... The colour bands signify the beginning of an international peregrine colour banding system established for quick geographical identification of banding locality. During the 2 summers, 9 gyrfalcon nesting cliffs were located in the survey area. We believe that at least 6 of the 9 locations were occupied in 1972. In 1973, 8 of the 9 cliffs were checked. Young were found at 4 sites. A fifth was observed from an aircraft and appeared to be active. Lone adults were observed at 2 other locations. Seven young gyrfalcons were banded out of 10 young found. One nest site was inaccessible and the young were not banded, accounting for the difference in number located and banded. The production rate per producing pair of gyrfalcons was 2.50 young. ... Our sample survey indicates that in 1973, as in 1972, the peregrine falcon reproduced normally in West Greenland. The slightly higher production rate in 1973 can possibly be attributed to warmer temperatures during the nesting period, as the summer of 1972 was unseasonably cool. However, the 1972 data on eggshell thinning and high DDE and PCB residues reveal that this population is precariously balanced, and severe reproductive failure threatens. Analysis of the 1973 addled egg and measurement of the additional eggshell fragments will supplement the 1972 results to provide a larger data base. ...