Decoy Trap Bias and Effects of Markers on Reproduction of Northern Pintails (Vicios en las Trampas con Señuelo y los Efectos de Marcadores en la Reproducción de Anas acuta)

• Published in: Journal of field ornithology 1999, Vol.70 (4), p.504-513
• Main Authors: Guyn, Karla L., Clark, Robert G.
• Format: Article
• Language: English
• Subjects: Anas acuta; Animal nesting; Animal traps; Backpacks; Bird nesting; Clutch size; Ducks; Eggs; Female animals; Radio transmitters; Waterfowl
• ISSN: 0273-8570; 1557-9263

Decoy traps have been widely used to trap waterfowl, but trap bias has rarely been examined. Likewise, researchers often radio-mark animals with the implicit assumptions that (1) radio-marked individuals are representative of the population and (2) transmitters do not alter behavior or other measures of interest. In this paper, we quantified possible trap bias, and combined effects of capture and radio-making, on attributes and reproduction of female Northern Pintails (Anas acuta). We found no difference in the age distribution or size of decoy-trapped versus nest-trapped female pintails. However, radio-marked females tended to lay fewer eggs than unmarked females. When analyses were restricted to first nests only, clutch-initiation dates did not differ between radio-marked and unmarked females. The number of ducklings hatched did not differ between radio-marked and unmarked females. Although we did not detect age or size differences between birds caught in decoy traps and those nest-trapped, it is unclear if either group is completely representative of the population. However, pintails were difficult to capture with decoy traps and the method was time and labor intensive. Our results suggest that the combined effects of trapping and marking may negatively affect some aspects of reproduction in pintails. /// Las trampas con señuelo se han utilizado ampliamente para atrapar aves acuáticas, pero rara vez se ha examinado el vicio de estas. Igualmente, los investigadores marcan a menudo los animales con radiotransmisores asumiendo implicitamente que (1) los individuos radio-marcados representan la población y (2) los transmisores no afectan la conducta u otras medidas de interés. En este trabajo cuantificamos los posibles vicios al usar trampas, y el efecto combinado de captura y marcar con radiotransmisores en los atributos y en la reproducción de Anas acuta. No hallamos diferencias en la distribución de edades o tamaño de hembras de Anas acuta atrapadas en trampas y las atrapadas en los nidos, sin embargo, las hembras con radiotransmisores tendían a poner menos huevos que las no marcadas. Al restringir los análisis a los primeros nidos, las fechas en comenzar la camada no difieren entre hembras marcadas con radiotransmisores y las no marcadas. Aunque no detectamos diferencias en las edades o tamaños entre las aves atrapadas en trampas con señuelo y aves atrapadas en el nido, no está claro si alguno de los grupos representa la población completa. De todas for