Post-mortem examinations of New Zealand birds. 3. Shining cuckoos (Chrysococcyx lucidus Aves: Cuculinae)

I examined 107 shining cuckoos that died accidentally in the northern North Island, New Zealand, during 39 years. Birds arriving on migration in spring were all in adult plumage. Juveniles occurred mainly from January to March. The sex-ratio of adults was 1:1. In several measurements, females were slightly larger than males on average, and adults slightly larger than juveniles. Gonad size suggested readiness for breeding from September to January (inclusive). Ninety-one gizzards held a total of 3754 arthropod food items. Insects (10 orders) made up around 94% of items and just two orders accounted for 79% of food items: caterpillars (larval Lepidoptera, 55%) and beetles (Coleoptera, 24%). 'Spiny' caterpillars made up roughly 8% of total caterpillars. Ladybirds (Coccinellidae) made up 21% of beetles. Shining cuckoos ate small prey, mostly 1-10 mm long (44%) and 11-20 mm long (43%). By eating hairy caterpillars and ladybirds, shining cuckoos exert predatory control on insects that other birds avoid. By gorging (up to 258 insects per stomach) the cuckoo might dampen the impact of herbivorous insects (e.g. caterpillar infestations) on plants.