The inverse relationship between body size and environmental temperature is a widespread ecogeographic pattern. However, the underlying forces that produce this pattern are unclear in many taxa. Expectations are particularly unclear for migratory species, as individuals may escape environmental extremes and reorient themselves along the environmental gradient. In addition, some aspects of body size are largely fixed while others are environmentally flexible and may vary seasonally. Here, we used a long‐term dataset that tracked multiple populations of the migratory piping plover Charadrius melodus across their breeding and non‐breeding ranges to investigate ecogeographic patterns of phenotypically flexible (body mass) and fixed (wing length) size traits in relation to latitude (Bergmann's Rule), environmental temperature (heat conservation hypothesis), and migratory distance. We found that body mass was correlated with both latitude and temperature across the breeding and non‐breeding ranges, which is consistent with predictions of Bergmann's Rule and heat conservation. However, wing length was correlated with latitude and temperature only on the breeding range. This discrepancy resulted from low migratory connectivity across seasons and the tendency for individuals with longer wings to migrate farther than those with shorter wings. Ultimately, these results suggest that wing length may be driven more by conditions experienced during the breeding season or tradeoffs related to migration, whereas body mass is modified by environmental conditions experienced throughout the annual lifecycle.

ABSTRACT. Collisions with wind turbines are an increasing conservation concern for migratory birds that already face many threats. Existing collision-risk models take into account parameters of wind turbines and bird flight behavior to estimate collision probability and mortality rates. Two behavioral characteristics these models require are the proportion of birds flying at the height of the rotor swept-zone and the flight speed of birds passing through the rotor swept-zone. In recent studies, investigators have measured flight height and flight speed of migrating birds using fixed-beam radar and thermal imaging. These techniques work well for fixed areas where migrants commonly pass over, but they cannot readily provide species-specific information. We measured flight heights of a nesting shorebird, the federally threatened Piping Plover (Charadrius melodus), using optical range finding and measured flight speed using videography. Several single-turbine wind projects have been proposed for the Atlantic coast of the United States where they may pose a potential threat to these plovers. We studied Piping Plovers in New Jersey and Massachusetts during the breeding seasons of 2012 and 2013. Measured flight heights ranged from 0.7 to 10.5 m with a mean of 2.6 m (N = 19). Concurrent visually estimated flight heights were all within 2 m of measured heights and most within 1 m. In separate surveys, average visually estimated flight height was 2.6 m (N = 1674) and ranged from 0.25 m to 40 m. Average calculated flight speed was 9.30 m/s (N = 17). Optical range finding was challenging, but provided a useful way to calibrate visual estimates where frames of reference were lacking in the environment. Our techniques provide comparatively inexpensive, replicable procedures for estimating turbine collision-risk parameters where the focus is on discrete nesting areas of specific species where birds follow predictable flight paths. RESUMEN. Estimación de altura y velocidad de vuelo de Charadrius melodus en reproducciónLas colisiones con turbinas de viento son un motivo de preocupación para la conservación de aves migratorias, las cuales ya tienen muchas amenazas. Los modelos de riesgo de colisión existentes tienen en cuenta parámetros de turbinas de viento y comportamiento de vuelo de las aves, para estimar la probabilidad de colisión y las tasas de mortalidad. Dos características comportamentales que estos modelos requieren, son la proporción de aves volando a la altura de la zona de barrido del rotor y la velocidad de vuelo de las aves pasando a través de la zona de barrido del rotor. En estudios recientes, investigadores han medidos la altura y velocidad de las aves en migración usando radares de haz fijo e imágenes térmicas. Estas técnicas tienen buen desempeño enáreas fijas donde las aves migrantes comúnmente pasan, pero no proveen información especifica para cada especie. Medimos la altura de vuelo de un ave playera en anidación que están federalmente amenazada, Charadrius melodus, usando buscadores de rangoópticos y medim...