Aug 112012
 

During July, two new papers were published under the project ‘Crossing the Caribbean’ – a SELVA project that aims to identify and prioritize the sites and habitats used by migratory birds in northern Colombia during migration. The first paper, published in the AUK, shows how a migratory thrush, the Veery, uses the Sierra Nevada de Santa Marta mountains (SNSM) in northern Colombia to accumulate energy for the next stage of their migration. Veery arrive at the SNSM during fall migration having crossed the Caribbean sea from North America. During their stay in the SNSM of approximately 10 days, they consume vast amounts of fruit, storing enough energy for a 2200 km towards their wintering grounds in Brazil. A stopover in the SNSM provides the energy required to complete almost 30% of this species fall migration, making the SNSM a critical site for a successful migration.

The second paper, published in the Journal of Ornithology, examines how three species of migratory thrushes and two species of vireos use the SNSM during both spring and fall migration. The most striking result, is that ecologically similar species do not pass through the SNSM at the same time. For example, the Veery is very abundant during fall migration but is effectively absent during spring migration. In contrast, the Gray-cheeked Thrush shows the opposite pattern, being principally a spring migrant. The same phenomenon can be seen in the two vireo species. The reasons why these species appear to avoid each other are not clear, however, competition in a highly energetically demanding part of the life cycle may be an important factor. 

Bayly, N.J., Gomez, C., Gonzalez, A.M., Hobson, K.A. & Rosenberg, K.V. (2012) Fall migration of the Veery (Catharus fuscescens) in northern Colombia: determining the energetic importance of a stopover site. The Auk 219(3): 449-459. PDF

Gómez, C., N. J. Bayly & K. V. Rosenberg. (2012). Seasonal variation in stopover site use: The case of Catharus Thrushes and Vireos in northern Colombia. Journal of Ornithology. Online Early DOI 10.1007/s10336-012-0876-5