Did you know that black kites, (Milvus migrans), which are on the Australian Transport Safety Bureau’s top 10 species struck list, are likely to be an even higher strike risk following record rainfall on Australia’s east coast so far this year? Avisure has already talked about the unique behaviour of black kites in the dry season in northern Australia where they use fire to hunt, thermalling in large numbers above the fires.
However, during rain it’s a different story. According to one Italian study, in heavy rainfall black kites’ hunting success reduced, while the energy expended flying increased. Rainfall and storms will therefore generally mean less kites seen flying.
It is in the months after above-average rainfall where the black kite population can increase dramatically, following a flush of prey and food. One study, in arid southwestern Queensland, showed increased numbers of diurnal raptors, including black kites, within three months of large rainfall. A second study, again of more arid regions of Queensland, showed rodent numbers ‘boomed’ 6 to 9 months after the first big rainfall. Similarly, insects are likely to respond to exceptional rain within weeks to months, with increased egg-laying, hatching and activity.
Above-average rainfall can also affect black kite breeding success. They can breed at any time of the year in northern Australia and so improved conditions will lead to more breeding, along with greater breeding success (the number of chicks each pair can raise to fledgling stage). Thus, above-average rainfall is likely to lead to increased numbers of kites in the following year.
With these rapid responses in prey populations and consequent rapid increase in kite numbers (through breeding as well as immigration), an exodus of kites and other raptor species can follow when the prey base collapses. These events are called irruptions and see numbers of kites and other species dispersing as far south as Melbourne.
Thanks to Dr Will Steele, for providing this information.
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