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 abl e to return to their nest burrows at night in complete darkness. Since petr els have a well-developed olfactory system, we carried out an experiment to test whether blue petrels use olfaction to localise their nest burrows, In cubating birds were injected intranasally with a zinc sulphate solution, wh ich reversibly impairs the sensitivity of the olfactory mucosa; control bir ds were treated with physiological saline solution. None of the anosmic bir ds returned to their burrows, whereas all the birds treated with saline sol ution did. Our results suggest that olfactory cues are necessary for blue p etrels to find their burrows.