Foraging movements of common noddies in the East Indian Ocean are dependent on breeding stage: implications for marine reserve design

Abstract

Increasingly, space use by foraging seabirds is being used as an indicator of ocean condition to inform projected planning for climate change, fisheries management and marine protected areas. We tracked foraging common noddies (Anous stolidus) from a colony in the East Indian Ocean using back-mounted solar GPS trackers during incubation and chick rearing to evaluate their suitability as biomonitors of ocean condition, and the overlap of flight tracks with marine protected area boundaries. This is the first study to track this species in its eastern distribution and across different stages of the breeding cycle. Six birds were tracked for 89 days in total, describing 10089km of flight. Birds made significantly longer trips during chick rearing, which may reflect reduced availability of prey. The tracking period coincided with a particularly strong ENSO event, which may have impacted foraging behaviour, but the foraging area was found to be at least 10000km2. Foraging was associated with the end points of outward trips that were generally at the edge of the continental shelf, or within proximity of canyon-like bathymetric features or current structures on the shelf. Birds foraged over the shelf during incubation, suggesting a greater reliance on food web structures associated with Leeuwin Current structures. Home ranges and movement tracks showed limited overlap with proposed marine park boundaries, but are promising as indicators of ocean productivity, suggesting that their role in the design of marine reserve networks in the future should be maximised.