Aim The role of migratory birds in the spread of parasites is poorly known, in part because migratory strategies and behaviours potentially affecting transmission are not easy to study. We investigated the dynamics of infection by blood parasites through the annual cycle of a long‐distance Nearctic–Neotropical migratory songbird to examine the role of this species in dispersing parasites between continents. Location The Americas. Taxon Grey‐cheeked Thrush (Catharus minimus, Aves, Passeriformes, Turdidae), Birds. Methods We used molecular and microscopy screening of haemosporidian parasites (Plasmodium, Haemoproteus, and Leucocytozoon) to examine the prevalence, distribution, and diversity of lineages through the annual cycle (breeding, migration, and wintering) of the grey‐cheeked thrush in North and Central America, Santa Marta mountains, the Andes, and the Amazon. We aimed to identify transmission areas, to examine the degree of sharing of haemosporidian lineages with resident birds in various areas and to assess the potential role of immunologically naïve juvenile individuals in parasite transmission. Results Prevalence and lineage diversity of haemosporidians varied significantly over time, being higher during breeding and fall and spring migration, and declining during wintering. Grey‐cheeked thrush shared few parasite lineages with tropical resident birds and slightly more lineages with other migratory and resident boreal species. We detected gametocytes in blood during spring migration stopover, but these were of lineages not found in resident tropical birds, indicating relapses of parasites transmitted elsewhere. Transmission likely occurs mostly on the breeding grounds, where juveniles and adults carried lineages restricted to closely related species of thrushes and other species of boreal birds. Main conclusions Long‐distance migratory songbirds are likely not important dispersers of blood parasites because there are ecological and evolutionary barriers to the interchange of parasites across vastly separated areas. Further work with thorough spatial and temporal sampling across other species, and considering the role of vectors, is necessary to understand the ecological and evolutionary factors explaining the distribution of parasites over broad scales.

Sonations are sounds that animals produce with structures other than the vocal apparatus for communication. In birds, many sonations are usually produced with modified flight feathers through diverse kinematic mechanisms. For instance, aeroelastic fluttering of feathers produces tonal sound when airflow exceeds a threshold velocity and induces flight feathers to oscillate at a constant frequency. The Fork-tailed Flycatcher (Tyrannus savana) is a Neotropical bird with both migratory and year-round resident subspecies that differ in the shape of the outer primary feathers of their wings. By integrating behavioral observations, audio recordings and high-speed videos, we find that male Fork-tailed flycatchers produce sonations with their outer primary feathers P8-10, and possibly P7. These sounds are produced during different behavioral contexts including: the pre-dawn display, intraspecific territorial disputes, when attacking potential nest predators, and when escaping. By placing feathers in a wind tunnel, we elicited flutter at frequencies that matched the acoustic signature of sounds recorded in the wild, indicating that the kinematic mechanism responsible for sound production is aeroelastic flutter. Video of wild birds indicated that sonations were produced during the downstroke. Finally, the feathers of migratory (T.s.savana) and year-round resident (T.s.monachus) Fork-tailed flycatchers flutter in feather locations that differ in shape between the subspecies, and these shape differences between the subspecies result in sounds produced at different frequencies.

Because space‐use patterns are a key aspect of the ecology and distribution of species, identifying factors associated with variation in size of territories and home ranges has been central to studies on population ecology. Space use might vary in response to extrinsic factors like habitat quality and to intrinsic factors like physical condition and individual aggressiveness. However, the role of these factors has been poorly documented in the tropics, particularly in high‐elevation bird species. We report the home‐range size of a Neotropical Andean bird, the gray‐browed brush finch (Arremon assimilis), and evaluate the role of physical condition in explaining variation in home‐range size among individuals. We performed spot mapping to estimate the home ranges of 14 territorial males in Bogotá, Colombia, using minimum convex polygons (MCP) and 95% kernel density estimators (KDE). The mean home‐range size estimated for the 100% MCP was 0.522 ± 0.305 ha (range = 0.15–1.18 ha), whereas the 95% KDE estimation was 0.504 ± 0.471 ha (range = 0.13–1.88). We calculated the real mass index of each bird as a proxy of physical condition to assess whether individuals in better physical condition had larger home ranges. Because we found no relation between our estimations of physical condition and home‐range size, we conclude that space use in this species might depend more on ecological factors such as habitat quality or neighbor density than on individual traits. Abstract in French is available with online material.