The reproductive and foraging behaviour of the African snipe (Gallinago nigripennis) (Bonaparte 1839) in Central Kenya
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Date
2012-01-20
Authors
Gichuki, Cecilia Muringo
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Abstract
This thesis gives the results of 34 months (March 1997 to December 1999) of field study of the African Snipe at Lake Ol' Bolossat (36° 26'E 00° 09'S) and surrounding highlands. The area is characterised by extensive destruction of marshes and catchment of the basin. The African Snipe is very sensitive to habitat destruction and can be a useful indicator of habitat quality. The aims of the study were to determine population characteristics, foraging behaviour and factors that influence reproductive success of the African Snipe. The focal animal-sampling technique and radio-tracking methods were used to study foraging behaviour and movement of marked and unmarked birds respectively. The relative age of individuals was determined from changes in pulmage and body size. The sex of adults was determined from cloacal examination and DNA analysis. The diet was investigated by observing foraging birds, analysing faecal material and potential food items collected at foraging sites.
There was a resident population of African Snipes that bred and foraged in the study area throughout the year which numbered 900 to 1200 birds. The mean population density was 14.7 + 0.17 birds km-2 and the average sex ratio of 1.24:1 was slightly skewed towards males, especially early in the breeding season. Whereas most of the snipes (86.7%) occurred in Lake Ol'Bolossat Basin, a few (14%) were found in upland marshes.
The study has shown that African Snipes are monogamous. Males performed distinctive aerial and ground displays, defended small breeding territories (<10 ha) and guarded the nest. The females selected the nest site, built the nest and incubated the eggs. Nests were in more elevated sites (mean 8.49 + 1.60 cm above water or ground), which were in shallower water (mean 3.51 + 0.47 cm) and in denser clumps of grass (mean 26.02 + 0.8 plants/m2) than random locations. Clutch size ranged from two to four with a mode of three eggs. The egg-laying dates (Julian Dates) varied significantly among pairs nesting in stream-marshes, lake-marshes, tall wet grassland and abandoned cultivation with mixed herbs (F 3,141 = 278, P<0.001). The incubation period ranged from 19 to 21 days and did not differ between nests built in different periods and sites. Hatching success ranged from 54 to 69% and varied significantly between pairs nesting in different periods and habitat types. The maximum hatching success of 1.98 + 0.14 hatchings per nest occurred in 1998 while minimum of 1.63 + 0.39 hatchings per nest occurred in 1997. The average fledging success of all pairs during this study was 1.26 + 0.47 fledglings per nest. The overall reproductive success of snipes breeding in the study area was estimated at 38.2% (146 juveniles/382 hatchlings), indicating that only one out of three chicks hatched survived to adult age.
African Snipes foraged in a wipe range of wet habitats within a mean home range size of 39.08 + 4.6 ha (n = 7 birds). Its diet mainly consisted of large invertebrates, particularly annelids (34.4%), crustaceans (20.7%), insect larvae (17.8%), and molluscs (5.8%). While searching for food and nest sites, the snipes moved in altitude from the lake basin (2340 m) to as high as Dundori Hills (2700 m). Recoveries of ringed birds indicated that most of the snipes made localized movements but a few vacated the study area for extended periods. During this study, a decline of about 34% of the African Snipe population was estimated in Kenya.
Description
A Thesis Submitted in Partial Fulfillment of the Requirements for the Award of the Degree of Doctor of Philosophy of Kenyatta University, 2002: The QL 696.C48G5
Keywords
Snipes--Africa