A party of swifts went through Freehold at very high speed very low due South, perhaps 30 birds this afternoon in driving rain. I can only assume these are from far further North, even Scandinavia. I did some reading. This is a fascinating recent paper (link below) discussing leapfrog and chain migration, terms I was previously unaware of. It made me think. Why do so many migratory birds overwinter in Southern climes yet breed in the Northern Hemisphere and not vice versa? I am struggling to think of anything excepting Antarctic breeders that travel South in the Southern Hemisphere Summer…. penguins, albatrosses etc. So why do almost all others breed in the Northern Hemisphere and rest over Winter far further South.
Also, if a swallow is capable of 2 or 3 nests between April and October, why doesn’t it breed twice a year, once in Europe and once in Africa? Why does the swift risk everything with huge weather affected losses breeding high in the Northern Hemispere when it would be more successful breeding twice in the Mediterrannean then Central Africa each year? That’s what another rainy day does to your head. More questions.
https://www.sciencedaily.com/releases/2020/09/200915105949.htm
