Determination of Clutch Size and the Breeding Biology of the Spur-Winged Plover (Vanellus spinosus) in Israel

Abstract

The breeding biology of the Spur-winged Plover (Vanellus spinosus) was studied in an agricultural area in central Israel from 1989 through 1993. The breeding season extended from March to September. The average clutch size was 3.4 eggs and modal clutch size was four eggs. Clutch size declined slightly during the season. Eggs were laid at about two-day intervals. The average incubation period was 28 days, but it declined during the season in correlation with increased ambient temperatures and laying order. In four-egg clutches the last egg was incubated 3.4 days less than the first. Hatching of a four-egg clutch was asynchronous and lasted 1.9 days. Field hatchability was 86.4% of all eggs laid. In the laboratory, the highest hatching success (97.7%) occurred at an incubation temperature of 37.5°C. Field experiments showed that in four-egg clutches incubation temperature was significantly higher, incubation periods tended to be shorter (but not significantly so), and hatching success was higher (but not significantly so) in comparison with artificially enlarged five-egg clutches. This lends some, but not unequivocal, support to the hypothesis that clutch size may be limited by incubation ability. However, females whose clutches were removed upon completion were capable of laying continuously without altering either clutch or egg size, suggesting that clutch size is not limited by egg-formation abilities.