Updated: Sep 7, 2020
Migration, genes and blackcap birds!
A Eurasian blackcap bird. Picture from wikimedia commons https://commons.wikimedia.org/wiki/File:Blackcap_1a_(6996063938).jpg
Blackcaps are birds found across Europe. A population of these birds in Europe migrates south-east in autumn and another population migrates south-west. But when birds from these two populations were crossbred, in which direction did the young ones fly?! The average direction the young ones flew in was intermediate between the direction taken by their parents! That is, on an average, they actually flew towards south!!
A representation of the directions in which the parents and the young ones flew. Red arrow is the average direction of migration of 1 parent, yellow arrow indicates average direction of the other parent. Orange arrow indicates average direction of migration of their young ones! Diagram taken from original research paper https://www.gwern.net/docs/genetics/selection/1991-helbig.pdf
This is one of the first studies which shows that along with other factors like the earth's magnetic field and use of prominent landmarks, genes and heredity can also play an important role in the direction an animal migrates in!
If anyone is interested in the original study, here is the original paper:
Reference: Helbig, Andreas J. "Inheritance of migratory direction in a bird species: a cross-breeding experiment with SE-and SW-migrating blackcaps (Sylvia atricapilla)." Behavioral Ecology and Sociobiology 28.1 (1991): 9-12.