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Reproductive parameters of Caspian Gull Larus cachinnans Pallas, 1811 in different habitats nearby and away fish ponds

Gwiazda R., Neubauer G., Betleja J., Bednarz Ł., Zagalska-Neubauer M.

Polish Journal of Ecology

2015

Vol. 63, nr 1

159--165

Reproductive performance of gulls depends on a variety of factors, but food abundance and its availability are among the most important. Clutch and egg sizes in gulls are found to be strongly influenced by food availability, thus better reproductive performance in the colony with greater fish availability (near fish ponds) was expected in that study. We compared the reproductive traits (clutch size, volume of eggs in the full clutch, relative volume of the C-egg (the third egg in gull’s clutches) and hatching success) of Caspian Gull Larus cachinnans in five inland colonies in Poland located at a gravel pit, a lake, a river and two dam reservoirs. Differences in the clutch size between sites were found, with the lowest at a lake. We found similar clutch volume in all studied colonies. C-eggs were slightly smaller than A- and B- eggs, in all colonies and all study years, but the relative volume of C-egg in colonies located near fish ponds (<10 km) was significantly greater compared to colonies located far away. This may be explained by high fish availability in fishponds in comparison to other habitats. However hatching success (the ratio of the number of hatched chick to the number of eggs laid) was highest in the colony at the lake. This indicates that both inland habitats a gravel pit and a lake offered good food conditions for large gulls when fish ponds are nearby.

Can poor foraging habitat (an inundated opencast sulphur mine) be attractive to the great crested grebe (Podiceps cristatus)?

Gwiazda R.

Oceanological and Hydrobiological Studies

2009

Vol. 38, No.3

135-139

During investigations of an inundated opencast sulphur mine (an open, deep water habitat with a relatively small littoral area) only five species of breeding water birds were recorded. The density of breeding great crested grebes Podiceps cristatus was relatively high (c. 1.0-1.1 pairs 10 ha-1 of water, and 1.6-1.8 pairs ha-1 of the macrophyte area) although fish density was very low. High water transparency probably compensated for low prey density, because potential prey could be readily detected. Most of the fish were small and occurred in the upper layers of the water column (they could not live below 10 m where the water was anoxic), so were readily available and easily caught by the grebes.