Is there more than one way to cross the Caribbean Sea? Migratory strategies of Nearctic‐Neotropical landbirds departing from northern Colombia

Abstract

For migratory landbird species, large expanses of open water or inhospitable areas provide unique challenges during migration. Research on the strategies that species use to navigate barriers can yield insights into the factors shaping the evolution of migration and facilitate the identification of critical staging areas prior to barrier crossing. One such barrier, the Caribbean Sea, has received little study but must be negotiated by ≈50 migratory landbirds as they fly from South America to North America in spring. Recent discoveries from the gray‐cheeked thrush Catharus minimus, which undertakes non‐stop flights >3000 km across the Caribbean Sea, raises the possibility that the breadth of potential strategies has been unappreciated thus far. We calculated fuel load and potential flight range in 9985 individuals of 16 species captured over 10 years at two stopover sites in northern Colombia to 1) evaluate the likely migratory strategy of these species as they depart northern Colombia in spring, and 2) evaluate the influence of family, diet, morphology and migratory distance on potential flight range. We found considerable variation in flight ranges and therefore strategies for crossing the Caribbean Sea/Gulf of Mexico barrier complex. In addition to gray‐cheeked thrush, non‐stop flights >2500 km were possible in yellow‐billed cuckoo Coccyzus americanus, yellow warbler Setophaga petechia and northern waterthrush Parkesia noveboracensis. The remaining species were either capable of over‐water flights to the Yucatan Peninsula/Cuba (>1800 km) or shorter flights to middle Central America (>1000 km) and likely required one or more stopovers to reach North America. Predicted flight ranges were influenced by morphology but not by distance, diet or taxonomic group, providing a novel insight into the evolution of migratory strategies. Our study confirms the vital role northern Colombia performs in providing energy for migratory birds and highlights the Caribbean as a key migratory barrier for many species.

A general theory of avian migratory connectivity

“…In addition, we assume that birds migrate along a straight line between breeding and wintering sites and that the cost of migratory movement is a linear function of the length of this straight line. However, birds usually migrate following more complex routes, involving stop‐overs and barrier avoidance (Cano et al, 2020; Delmore et al, 2012; Irwin & Irwin, 2005; Norevik et al, 2020; La Sorte et al, 2016), and are affected by environmental conditions along the way such as wind (Kranstauber et al, 2015; Norevik et al, 2020). These, in turn, might affect the energetic cost associated with relocating between seasonal grounds and therefore impact model predictions.…”

The interplay of wind and uplift facilitates over-water flight in facultative soaring birds

“…As a result, our findings can further shed light on the energy seascapes other animals flying over these flyways would encounter. For example, the relatively high uplift during the night compared to daytime ( figure 2 ) means less drag and could lead to energetically cheaper flight in nocturnal migrants over the Mediterranean Sea [ 54 , 55 ] and the Caribbean Sea [ 56 , 57 ] (but see [ 58 ] for a suggestion that songbirds prefer non-turbulent air for sea-crossing). Moreover, dragonflies [ 59 ] and cuckoos ( Cuculus spp.)…”

A place to land: spatiotemporal drivers of stopover habitat use by migrating birds

“…Geographical patterns in SPR may be the result of species and population‐specific site selection; for example, the high eastern spring values could reflect the routes of birds from South America making first landfall after non‐stop flights (Cano et al ., 2020). Migrants from South America can make first landfall as far inland as the Central US and southern Canada, although most stop along the Gulf of Mexico coast (Gómez et al ., 2017).…”