Col de Bretolet

The Col de Bretolet is located on a bird migration route through which many thousands of birds pass, especially from early August to late October, with many travelling at night. In 1958 a long-term bird ringing program began in order to monitor autumn migration in the Swiss Alps and study energy metabolism, passerine moult and changes in migration patterns in relation to global climate change, as well as documenting irruptions of jays, tits and finches, comparing data with other ringing sites elsewhere and educating ringers.

Birds are caught both by day and at night in mist nets as they fly through the pass. On foggy nights the birds are attracted to the nets with the use of bright lights. As well as birds, bats are caught, and the pass is also well known for the migration of insects, notably moths and hoverflies.

• Jenni, Lukas; Kéry, Marc (2003). "Timing of autumn bird migration under climate change: advances in long-distance migrants, delays in short-distance migrants". Proceedings of the Royal Society B. 270 (1523): 1467–1471. doi:10.1098/rspb.2003.2394. PMC 1691393. PMID 12965011.
• "Col de Bretolet". World Database on Protected Areas. WCPA. August 2004. Retrieved 15 February 2010.^{[permanent dead link‍]}
• "Long-term surveillance of bird migration on Col de Bretolet". Swiss Ornithological Institute. Retrieved 15 February 2010.