The male Indian Roller, Coracias benghalensis, attracts females by flying high in the sky. The bird rolls and falls in a circular motion, flapping wings and screaming. This mid-air courtship dance never fails to amaze!
But the behaviour is seen only in the mating season. What are the seasonal changes in the brain responsible for this behaviour?
Navigation in space is coded in the hippocampus, a complex structure in the brain. In birds, the dorso-medial hippocampus is responsible for spatial learning and landmark navigation.
So how does the morphology of the dorso-medial hippocampus change during the breeding season?
Kirti Ojha and K. P. Singh, from Allahabad University, recently came up with some answers. They caught adult male birds in breeding and non-breeding seasons and confirmed the reproductive stage by observing the growth and development of the testes.
The duo examined samples of hippocampal tissue under a microscope for any changes in neurons in the dorso-medial hippocampus. They observed considerable increase in neuronal morphometric parameters during the breeding season.
“Seasonal neuronal plasticity in the hippocampal complex enhances cognitive performance, especially navigation in birds”, says Kirti Ojha.
Further studies on the variations in hormones and neurochemical parameters are needed to fully understand these relationships, say the researchers.
In morphology and function, the hippocampus is more or less the same in birds and animals. So, could the seasonal variations reported in human birth rates, especially in higher latitudes, be due to behavioural changes caused by morphological changes in our hippocampus?
Aneesh Kumar K. V.
Sacred Heart College, Kochi
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