![]() ![]() Depending on the foraging habitat, this species feeds on crustaceans, fish, small cephalopods and soft-bodied invertebrates by surface-seizing, dipping or pattering (flying very slowly near the surface of the ocean with the feet touching the water) ( Brooke, 2004). The Leach's storm petrel is one of the smallest procellariiforms (weight ca 38–54 g), and occurs in both the Atlantic and Pacific oceans. To test this prediction, we performed comparative anatomical investigations of the visual systems of two sympatric species occurring in the Northern hemisphere that use these different foraging strategies – the burrow-nesting DMS-responding Leach's storm petrel ( Oceanodroma leucorhoa), and the surface-nesting DMS non-responding northern fulmar ( Fulmarus glacialis). This result may reflect the fact that both species rely on olfaction for their nocturnal foraging activity, but northern fulmars might use vision more during daytime. The prediction that burrow-nesting DMS-responding procellariiforms should differ from non-responding species nesting in the open holds true for spatial resolution, but not for optical sensitivity. Both species have extended visual streaks with a central area of highest spatial resolution, but only the northern fulmar has a central fovea. These results suggest that under similar atmospheric conditions, northern fulmars have six times the detection range for similarly sized objects. However, the optical sensitivity of rod photoreceptors is similar between species. From the retinal ganglion cell density and photoreceptor dimensions, we determined that Leach's storm petrels have six times lower spatial resolution than the northern fulmars. Here, we used Leach's storm petrel, a DMS-responder, and northern fulmar, a non-responder, as model species to test this hypothesis on their sensory ecology. Together these results suggested that differences in life-history strategy might also be linked to differences in visual adaptations. Burrow nesters also tended to be smaller and more cryptic, whereas surface nesters were larger with contrasting plumage coloration. Burrow nesters tended to track prey using dimethyl sulphide (DMS), a compound associated with phytoplankton, whereas surface-nesting species did not. Previous studies have found that life-history strategy (burrow versus surface nesting) was correlated to foraging strategy. Procellariiform or ‘tubenosed’ seabirds are challenged to find prey and orient over seemingly featureless oceans. ![]()
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