The extraordinary abilities of birds to migrate over large distances and return to the same breeding site every year have long been a source of wonder.
In the Bible, the prophet Jeremiah was able to point to the contrast between the birds of Israel, which faithfully kept to their migratory patterns year after year, and the people of Israel, who could not discern the timing of God’s actions:
“Even the stork in the heavens knows her appointed times; and the turtledove, the swift, and the swallow observe the time of their coming. But My people do not know the judgment of the LORD” (Jeremiah 8v7, NKJV).
Now studies by scientists from the University of East Anglia, UK, have unearthed another remarkable example, in the behaviour of black-tailed godwits, wading birds many of which breed in Iceland. It had been assumed that the birds, which are long-lived and pair for life, migrated from the breeding area to their winter feeding grounds together. But when the birds were ringed and tracked it emerged that they invariably split up and wintered hundreds of miles apart. The females flew off first, leaving the males to tend the growing chicks for a few more days. Then the males themselves set out, but to totally different sites.
One typical pair, nicknamed Gretar, a male, and Sigga, a female, breed at Holfi in southern Iceland. Sigga, however, spends the winter on the Humber Estuary near Hull in eastern England, while Gretar travels to the Algarve in Portugal, some 1,200 miles away. In the case of another couple, Gunnar the male winters in Essex, UK, whilst his mate Elsa travels to Spain. The team did not find a single case of paired birds in the same migrating flock.
However, the most striking feature of their behaviour is that in the spring, despite this long separation, the birds return to their Iceland breeding area within days of each other. According to the co-author of the study, “they manage to synchronise their arrival with astonishing accuracy”. The return of the godwits is spread over a whole month, from mid-April to mid-May, yet previously paired birds arrive within three days of each other. Only rarely do they fail to meet at the right time, and then unmatched birds may well find themselves a new mate.
Thus the synchronised arrival is of great importance to breeding success, but scientists currently have no idea how the birds manage to achieve it. They speculate whether paired birds could share genetic or physiological similarities, or utilise favourable weather systems for the final stages of their journey home, but essentially this ability remains an enigma.
Like so many other wonders of the living world, it testifies to the wisdom of the Creator and the complete inability of evolution to account for the origin of such mysteries.