Could osmotaxis explain the ability of blue petrels to return to their burrows at night?

Like many other species of petrel, blue petrel (Halobaena caerulea) are able to return to their nest burrows at night in complete darkness. Since petrels have a well-developed olfactory system, we carried out an experiment to test whether blue petrels use olfaction to localise their nest burrows. Incubating birds were injected intranasally with a zinc sulphate solution, which reversibly impairs the sensitivity of the olfactory mucosa; control birds were treated with physiological saline solution. None of the anosmic birds returned to their burrows, whereas all the birds treated with saline solution did. Our results suggest that olfactory cues are necessary for blue petrels to find their burrows.