Columbus beaten again, by the migration of a songbird!
When he set of for, "The Indies," little did Columbus know what had preceded him. In fact this early colonist beats him by two totally opposite routes (see the amazing feat on the map) and hundreds of thousands of years. The tiny wheatear (Oenanthe oenanthe) ranges far and wide across the Palaearctic. Because of this complete northern distribution, it has proved impossible so far to prove where the American populations over-winter.
Now it can be sung from the rooftops that Alaska to east Africa and eastern Canada to western Africa is the standard economy run for a 25g insectivorous bird with a huge appetite for trans-oceanic travel. German, English and Canadian ornithologists, led by Franz Bairlein carefully sought to provide the final proof of this largest journey by any bird with respect for its size. They publish their study Cross-Hemisphere Migration of a 25g Songbird today in The Royal Society Journal Biology Letters.
The feathers of breeding birds were used to confirm the origins of the wheatear with stable-hydrogen isotope analysis. Amazingly, these birds all seemed to link the African savannah ecosystems with the New World Arctic. Basic geolocation consisted of 1.2g locators with tiny 13mm sensors, sticking out at angles of 30o. Thirty northern wheatears from Alaska and sixteen from Baffin Island wore a harness made up the weight to 1.4g. Of the Alaskan 30, only 5 returned and even worse, one would not allow itself to be captured and another lost its geolocator.
The 3 birds that cooperated showed the Uganda/Kenya border and Sudan were their holiday destinations. Autumn saw them in Kazakhstan, then the Arabian Desert after a mean of 91 days. In the spring, only 55 days were taken. The northern wheatears from Canada were relatively less stressed. But they still took a trip that only returned two birds (with one lost geolocator). The one reporting bird crossed to western Britain in 4 days, then to Africa, on the Mauritanian coast in 26 days.
Spring saw a similar choice of locations, but the wind may have been against them, with a 55 day travel time. The simply staggering choice of overwintering habitat is only slightly confused with some central African choices by one or two birds. Otherwise, both sets of measurements prove the Canada/Mauritanian journey of one bird and the Alaska/Sudan trip of the other three are absolutely typical. Confirmation also came from colour-ringed birds which were tagged at the same time.
In the Pleistocene, we must remember that the Atlantic was narrower, making the innate migration pattern easier to establish. It still does not explain how the fledgling above still struggles across oceans and mountains with no experience and little reserves of body mass. If only birds could be given Olympic gold.
Migration routes and wintering grounds of three northern wheatears breeding in Alaskan (AK) and one in the eastern Canadian Arctic (CN; grey dot, breeding area, blue, autumn migration, orange, spring migration, dashed lines indicate uncertainty in migration routes close to equinoxes). Fifty per cent kernel densities of winter fixes (beginning of December 2009-end of February; purple, bird AK-1; green, bird AK-2; orange, bird AK-3; blue, bird CN-1) are given depending on the sun elevation selected (with 228 for most southern and with 24.58 for most northern densities). Pie charts indicate the proportion of individuals (AK: n 1/4 9, CN: n 1/4 4) originating from one of the three pre-defined wintering regions (red, western; orange, central; yellow, eastern) [8] based on stable-hydrogen isotope (dD) values in winter grown feathers and the dD values within each wintering region (mean+s.d. shown); Credit: F. Bairlein et al. 'Global migration of wheatears' (doi:10.1098/rsbl.2011.1223) in Biology Letters
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