Can Lanchester's Laws Help Explain Interspecific Dominance in Birds?

Abstract

We studied the applicability of Lanchester's laws of combat to explain interspecific dominance in birds. We focused on 10 species of Australian birds in the arid zone of New South Wales that foraged at an established locust trap. Consistent with the “linear law,” larger species usually dominated smaller species in one-on-one encounters. We found no support for the “N-square law,” which predicted that large numbers of smaller species could dominate larger species when more abundant. Further analysis of the most abundant species revealed that it was less likely to visit the locust trap when larger, more dominant heterospecifics were present. Body size, and not numerical superiority, seems to be an important determinant in interspecific foraging decisions in birds.¿Puede la Ley de Lanchester Ayudar a Explicar la Dominancia Interespecífica en Aves?Resumen. Hemos estudiado la aplicabilidad de las leyes del combate de Lanchester en explicar la dominancia interespecífica en aves. Hemos focalizado este estudio en 10 especies de aves australianas de la zona árida de New South Wales, las cuales se alimentaron en trampas de insectos establecidas para tal fin. Consistente con la “ley lineal,” las especies de mayor tamaño usualmente dominaron a las especies más pequeñas en los encuentros uno a uno. No encontramos evidencia que apoye la “ley cuadrática,” la cual predice que un gran número de especies de pequeño tamaño podrían dominar a especies de tamaño mayor cuando las primeras son más abundantes. Posteriores análisis sobre la especie más abundantes revelaron que la probabilidad de visita a las trampas de insectos es menor cuando individuos heteroespecíficos más grandes y más dominantes están presentes. El tamaño corporal, y no la superioridad numérica, parece ser un importante factor en las decisiones de forrajeo en las aves.

Dietary Overlap and Foraging Competition Between Mourning Doves and Eurasian Collared-Doves

“…Recent studies have applied Lanchester's (1916) laws, developed for human warfare during World War I, to interspecific interactions between species (Franks andPartridge 1993, Shelley et al 2004). Asymmetrical competition between species is addressed by Lanchester's linear law, which states that stronger (i.e., larger) individuals will win in a one-on-one battle (Lanchester 1916, Franks and Partridge 1993, Shelley et al 2004. Although this law agrees with the accepted view of asymmetrical competition, it was not supported in our study.…”

“…We only tested 1 or 2 doves of each species together. Lanchester's N-square law (Lanchester 1916, Franks and Partridge 1993, Shelley et al 2004) states that larger groups of individuals can overcome smaller groups, regardless of the relative body size of individuals. If applicable in an ecological context, this suggests that the potential for displacement of mourning doves and other native species by collared-doves may increase with increasing collared-dove numbers.…”

“…Perhaps, this dominance stems from the larger body size in collared-doves (x ¼ 206 g and 197 g for males and females, respectively; Romagosa 2002) than in mourning doves (x ¼ 130 g and 123 g for males and females, respectively; Mirarchi and Baskett 1994). Larger species, generally, are competitively superior to smaller species in asymmetrical, competitive interactions (Schoener 1983, Shelley et al 2004. Recently, Christmas Bird Count data from Cedar Key, Florida, USA, showed declining trends in mourning dove populations after Eurasian collareddoves arrived and increased in numbers, suggesting displacement of mourning doves by collared-doves (Stedman 1998).…”

Food‐niche differentiation in sympatric HenCircus cyaneusand Montagu's HarriersCircus pygargus

“…Body size influences the absolute energetic requirements of each species, and the outcome of aggressive interactions. Larger body size might give an advantage in interspecific agonistic encounters (Robinson‐Wolrath & Owens 2003, Shelley et al . 2004) but a disadvantage if food resources are limited, because larger body size implies larger food requirements (Nagy 1987, Julien‐Laferriere 1999).…”

“…Body size influences the absolute energetic requirements of each species, and the outcome of aggressive interactions. Larger body size might give an advantage in interspecific agonistic encounters (Robinson-Wolrath & Owens 2003, Shelley et al 2004) but a disadvantage if food resources are limited, because larger body size implies larger food requirements (Nagy 1987, Julien-Laferriere 1999. Therefore, food partitioning by prey size might occur between species that differ in body size (Ricklefs 1973, Jaksic & Braker 1983, with larger prey expected with increasing body size of the predator (Marti et al 1993).…”