Food availability and the timing of breeding in Snares Island snipe
- Department of Zoology, University of Canterbury
Breeding of New Zealand Snipe (Coenocorypha aucklandica) in relation to food supply was studied intensively on the Snares Islands over two breeding seasons, and the start of a third. About 20 territories were mapped each year by plotting sightings of colour-branded snipe, using a 20 m grid within the 7.5 ha study area. Areas of the 7 predominant ground covers within each territory were calculated by assessing ground cover within each 400 m2 grid square. Weekly food abundance (kJ/m2) in each ground cover was measured by soil sampling and bomb calorimetry. Cost of food extraction by snipe was calculated by measuring soil compaction (kg/cm2) in each ground cover each week, then converting this value to the energy (kJ) required to intensively probe 1 m2. Egg-laying dates for 38 first breeding attempts were spread over about 10.5 weeks each breeding season. Snipe commenced breeding earlier when November prey abundance was high. Peaks in energy availability (abundance minus cost of extraction) within each territory will be compared with laying and hatching dates to determine whether snipe raise their young when prey were most easily obtained.