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Unhatched Eggs in Swainson's Hawk Nests
| Content Provider | Semantic Scholar |
|---|---|
| Author | Houston, Charles S. |
| Copyright Year | 2004 |
| Abstract | --Unhatched eggs were recorded during banding visits to 987 nests of the Swainson's Hawk in western Saskatchewan between 1972 and 1988. In 104 of these nests there were 129 unhatched eggs, representing 10.5% of the nests and 6.3% of the eggs. Twentysix of the unhatched eggs (20%) contained visible embryos. Although this hawk migrates through Central and South America, where DDT is still widely used, the organochlorine residue and PCB content of unhatched eggs collected from nests in the Canadian Prairies in 1984 and 1985 were low. The percentage of unhatched eggs was highest in 1985, the peak year for grasshopper abundance and use of insecticides for grasshopper control. HUEVOS SIN ECLOSIONAR EN NIDOS DE BUTEO SWAINSONI Sinopsis.--Entre 1972 y 1988, se tomaron datos sobre huevos sin eclosionar de 987 nidos de Buteo swainsoni estudiados en el oeste de Saskatchewan. En 104 de estos nidos, se encontraron 129 huevos sin eclosionar, lo que representa al 10.5% de los nidos y 6.3% de los huevos, respectivamente. Ventiseis (20%) de los huevos que no eclosionaron contenian embriones. Este halcGn migra a travGs de Centro y Sur AmGrica, en donde todavla se utilizan insecticidas como el DDT. No obstante, los residuos de organoclorinados y contenido de PCB en los huevos coleccionados entre 1984-1985 resultaron ser bajos. E1 porcentaje de huevos sin eclosionar esult6 mils alto durante el 1985, afio en donde hubo un pico en la abundancia de saltamontes y mayor uso de insecticidas para el control de estos. Ecological and sociobiological factors affecting the hatchability of wild bird's eggs have been discussed by Koenig (1982) and Rothstein (1973). Remarkably little has been written about unhatched eggs of wild raptors, although Cameron (1913) observed the common presence of unhatched eggs in nests of the Swainson's Hawk (Buteo swainsoni). One of us (CSH) has recorded unhatched eggs in 987 Swainson's Hawk nests in Saskatchewan since 1972. The annual frequency of occurrence varies widely. In 1985, a peak year in a major grasshopper outbreak, when 3.6 million ha of cropland in Saskatchewan were sprayed with short-lived neurotoxic pesticides to control grasshoppers, we were alarmed at the higher frequency of unhatched hawk eggs. In the past, widespread use of insecticides, mainly dieldrin, to control grasshoppers, led to marked population declines of the Merlin (Falco columbarius richardsonii) and the |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://sora.unm.edu/sites/default/files/journals/jfo/v062n04/p0479-p0485.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
