Jun 09 2015
Though you may not have noticed, wood thrushes aren’t as plentiful as they used to be. According to the Second Atlas of Breeding Birds in Pennsylvania, “they are down by almost half since 1966 … though they remain widespread.”
The change is due to loss of breeding habitat (suburban sprawl for instance), acid rain (which affects their breeding success), and an interesting fact we learned a few years ago.
A team from the University of York headed by Bridget Stutchbury has conducted a long term study of wood thrush migration. Using geolocators they’ve tagged wood thrushes on both their breeding and wintering grounds to find out where the birds go and how long it takes them to get there. In 2009 they reported that wood thrushes take their time going south but are quick to return in the spring taking only two weeks to get ‘home.’
The data also revealed that regional populations of wood thrushes stick together on both their wintering and breeding grounds. Birds that breed in Crawford and Erie Counties, Pennsylvania spend the winter together in a small section of eastern Honduras and Nicaragua. Birds that breed in Vermont spend the winter at one location in Nicaragua. The map below from the study’s press release shows a star for each tagging site and round circles for the birds’ destinations. Notice that Pittsburgh’s birds spend the winter in Belize.
Now that we know where the wood thrushes go it’s easier to find out what’s happened. If the one place your region’s wood thrushes spend the winter is logged, fewer will survive to return in the spring.
That’s how deforestation in Central America affects your wood thrush.
Check the maps for yourself on page 9 of the study –> here.
p.s. Louisiana: This study also found that in the spring all wood thrushes cross the Gulf of Mexico and land at one specific spot near New Orleans. If that spot goes bad, it’s bad news for wood thrushes!