Foraging individuals optimize spatial movement to maximize resource use in heterogeneous environments. Colonies of Eciton burchellii, a neotropical species of army ant, forage as an army, consuming broad arrays of arthropod and social for E. burchellii and may encourage colonies to avoid contact with recently raided areas. Colonies are known to turn in opposite directions more often than random from previous days' foraging paths, which increases distances between recently raided areas. However, no evidence of colony avoidance of areas recently foraged by a conspecific colony has been presented. In this study, we analyze data collected in the Peruvian Amazon between 1998 and 2008 to examine colony spatial distribution using nearest-neighbor distance data. We found that colonies optimize movement by choosing foraging angles that deflect away from areas recently raided by conspecific colonies. In addition, we found that the observed nearest neighbor distance between E. burchellii colonies was more significant than expected if colonies were dispersed randomly. This dispersion pattern increases the distance between colonies and contributes to a spatial movement that optimizes foraging and decreases colony interactions at recently raided areas.

The global decline of songbird populations is a well-recognized conservation issue. Domestic cats kill an estimated 2.4 billion birds each year in the United States alone-more than most other anthropogenic threats combined. As many pet owners are reluctant to keep their cats inside, collar-mounted antipredation devices for domestic cats may be an important conservation tool. We examined the effectiveness of the Birdsbesafe (R) collar cover (BCC), a sleeve of brightly patterned fabric worn over a typical breakaway collar. The BBC's designers intend for the collar's bright colors to alert potential prey to the cat's presence. By combining data from two studies in New York (2014 and 2019) and one in Florida (2019), all of which used similar methods, we tested the hypothesis that the BCC effectively reduces avian mortality caused by cats of different ages and sexes in different hunting environments. We tested 94 cats over a 12-wk period in New York in 2014 or 8-wk periods in Florida and New York in 2019 during the bird breeding seasons; cats alternated 2-wk periods with and without the collar. Across studies, we recovered 2.7 times fewer birds per cat with the BCC than without (P = 0.006). The BCC was more effective at a temperate latitude than a subtropical one (P = 0.047). There was no difference in the effectiveness of the BCC for cats of varying ages, sexes, or hunting environments. Our results suggest that the BCC could be one tool within a larger effort to decrease domestic cat predation of songbirds.

Domestic cats are arguably the greatest anthropogenic threat to songbirds that currently exists, aside from habitat alteration and/or destruction (Loss et al. 2013). Although numerous campaigns have pushed for “cats indoors,” many cat owners are unwilling or unable to keep their pet cats indoors (American Bird Conservancy 2015). In rural New York, where many people keep farm animals, there is also a sizable population of barn cats that are kept specifically as outdoor pets to keep barnyard mouse populations in check. Although some owners choose to ignore the carnage their cats are inflicting on local birdlife, many others do in fact care about the barn swallows, savannah sparrows, and bluebirds that their barn cats are killing, as well as the backyard warblers, grosbeaks and catbirds in villages and hamlets across the North Country and the Adirondacks.

The domestic cat (Felis catus) has been described as the largest anthropogenic threat to songbird populations in North America. We examined the effectiveness of a novel cat collar in reducing avian and small mammal mortality by cats. The 2-inch wide Birdsbesafe® collar cover (CC) is worn over a nylon quick-release collar, and the bright colors and patterns of the CC are hypothesized to warn birds of approaching cats. We conducted two seasonal trials, each lasting 12 weeks, in autumn 2013 (n=54 cats) and spring 2014 (n=19 cats). Cats were randomly assigned to two groups, and CCs with interior collars were removed or put on every two weeks, to control for weather fluctuations and seasonal change. Cats wearing Birdsbesafe® CCs killed 19 times fewer birds than uncollared cats in the spring trial, and 3.4 times fewer birds in the fall. Birdsbesafe® CCs were extremely effective at reducing predation on birds. Small mammal data were less clear, but did decrease predation by half in the fall. The Birdsbesafe® CC is a highly effective device for decreasing bird predation, especially in the spring season. We suggest that the CCs be used as a conservation tool for owned as well as feral cats.

Foraging army ants face a problem general to many animals—how best to confront resource depletion and environmental heterogeneity. Army ants have presumably evolved a nomadic lifestyle as a way to minimize re-exploitation of previously foraged areas. However, this solution creates a challenge for an army ant colony: foraging by this colony and others creates a shifting landscape of food resources, where colonies should theoretically avoid their own previous foraging paths as well as those of other colonies. Here, we examine how colonies exploit this resource mosaic, using some of the optimality arguments first proposed and tested by Franks and Fletcher (1983), but with much larger data sets in a new location in SW Amazonia. Our data supported Franks and Fletcher’s (1983) model for systematic avoidance of raided areas during the statary phase, as well as a hypothesis of distance optimization between successive statary bivouacs. We also test and find significant evidence that foraging raids turn in opposite directions from the previous day’s directional angles more frequently than what would be expected if turning angles were distributed at random, which acts to move a colony away from recently exploited areas. This implies that colonies follow a straighter line path during the nomadic phase as opposed to a curved one, which acts to maximize distance between statary bivouacs. In addition to intra-colony movement optimization, we examine evidence for inter-colony avoidance from more than 330 colony emigrations and suggest that colony-specific pheromones are not necessarily repulsive to other colonies. Lastly, we compare our results with those of similar studies carried out at Barro Colorado Island (BCI), Panama. Despite a higher density of army ants in the SW Amazon region, colonies spend less time emigrating than their counterparts at BCI, which suggests a higher prey density in SW Amazonia.

Unlike most social insects, Eciton burchellii army ants cannot thermoregulate through nest construction. Instead, army ants thermoregulate behaviorally by creating a living nest (bivouac), shifting its position and structure, and potentially through nest site selection. We hypothesized that bivouac site selection is critical to E. burchellii colony survival. We predicted elevation above sea level, with associated variation in local abiotic environments, would affect bivouac site selection by E. burchellii colonies. We also expected nest sites to buffer against ambient variation in abiotic conditions. We recorded bivouac site choice by E. burchellii colonies at sites ranging from lowland wet forests to montane forests and reviewed previously published data. We measured microclimatic variables associated with nest sites in high-elevation montane forests: temperature, relative humidity, and light levels. Bivouac site selection varied with elevation: as elevation increased, fewer bivouac sites were exposed, more were underground, and fewer were elevated (in trees). High-elevation bivouac sites moderated diurnal temperature variation and had higher relative humidity levels and lower light levels than ambient conditions. The buffering of ambient temperature and humidity decreased with elevation in montane forests, suggesting that abiotic extremes in bivouac sites at the highest elevations may contribute to the upper elevational range limits of E. burchellii.

Five species of obligate ant-following birds--Phlegopsis nigromaculata, Myrmeciza fortis, Rhegmatorhina melanosticta, Gymnopithys salvini (Thamnophilidae), and Dendrocincla merula (Dendrocolaptidae)--and two species of army ants (Eciton burchelli and Labidus praedator) were studied in Amazonian Peru over five years. Here, I explore aspects of species coexistence in these five ecologically similar birds through analyses of their population ecology, resource use, behavior, and spatial movement patterns. Mean home-range size of each antbird species was reduced through reliance on the unpredictable but abundant foraging opportunities at L. praedator swarms. This little-known ant species played a pivotal role in expanding the foraging resource available to the obligate antfollowing birds, which allowed an increase in the birds' population densities well above what would be supported solely by the better-known E. burchelli army ants. Two of the five bird species (D. merula and M. fortis) displayed resource selectivity among antswarms by foraging significantly more with one of the two ant species. The woodcreeper D. merula further segregated from the four antbirds in its utilization of white-lipped peccary (Tayassu peccari) herds as a foraging resource; the peccaries act as "beaters" of arthropod prey in a manner similar to that of the army ants. The three antbirds that did not prefer one army ant species over the other (P. nigromaculata, R. melanosticta, and G. salvin 0 segregated by body mass, which may allow differential use of space along the width of an antswarm front. That size difference would permit a smaller, more subordinate species to "fit" along the front of a swarm that was already "full" to a different bird species. Population dynamics of the birds were not stable over five years of data collection, and total population of obligate ant-followers declined by almost half over the course of the study. It is suggested that periodic population fluctuations are a normal occurrence in guilds of obligate ant-followers and may be exacerbated by the lack of territoriality exhibited by most of these species. Lower population density correlated with decreased interference competition among individuals. Population fluctuations may increase the ability of the subordinate species R. melanosticta to coexist with the larger, dominant P. nigromaculata in floodplain forest. Nest-site selection may contribute to niche breadth among the obligate ant-followers. I provide descriptions of the nests, eggs, and nestlings of P. nigromaculata, R. melanosticta, nd G. salvini, which were undescribed at the start of the present stqdy. Received 22 November 2003, accepted 3 February 2004. RESUMEN.--$e estudiaron cinco especies de aves que siguen hormigas arrieras-Phlegopsis nigromaculata, Myrmeciza fortis, Rhegmatorhina melanosticta y Gymnopithys salvini (Thamnophilidae) y Dendrocincla merula (Dendrocolaptidae)--y dos especies de estas hormigas (Eciton burchelli y Labidus praedator) en la Amazonia peruana durante cinco aftos. En este trabajo se exploran aspectos de la coexistencia de estas cinco especies eco16gicamente similares por medio de analisis de su ecologla poblacional, uso de recursos, comportamiento y patrones espaciales de movimiento. E1 tamafio promedio del rango de hogar de cada especie de Thamnophilidae rue reducido por su dependencia en las impredecibles pero abundantes oportunidades de forrajear que brindan los ej•rcitos de L. praedator. Esta especie de hormiga jug6 un papel determinante para expandir los recursos disponibles para las aves, lo que permiti6 un incremento en la densidad poblacional de •stas m•is all•i de los niveles que podrian mantenerse finicamente con las hormigas de la especie E. burchelli. Dos de las cinco especies de aves (D. merula y M. fortis) exhibieron selectividad e recursos hE-mail: susan@phlegopsis.com 2 ORNITHOLOGICAL MONOGRAPHS NO. 55 entre legiones de hormigas, forrajeando signficativamente mils junto a una de las dos especies de hormigas. Ademfis, el trepatronco D. merula se segreg6 eco16gicamente d las otras cuatro especies de aves en t6rminos de su utilizaci6n de manadas de huanganas (Tayassu peccari) como recurso de forrajeo; estos animales espantan artr6podos que pueden ser depredados por las aves en una forma similar a como lo hacen las hormigas arrieras. Las tres especies que no prefirieron una especie de hormiga sobre la otra (P. nigromaculata, R. melanosticta y G. salvini) se segregaron en t6rminos de su peso corporal, lo que podrla perrnitir un uso diferencial del espacio en el frente de avance de los ejfircitos de horrnigas. Las diferencias de tarnafio podrlan permitir que las especies mils pequefias y subordinadas puedan acomodarse en el frente de un ej6rcito que ya estarla 11eno para individuos de otra especie. Las dinfimicas poblacionales de las aves no fueron estables a trav6s de los cinco aftos de toma de datos, y el total de la poblaci6n de aves seguidoras de hormigas declin6 a casi la mitad durante el curso del estudio. Se sugiere que las fluctuaciones poblacionales peri6dicas son eventos normales en los gremios de aves que siguen hormigas obligatoriamente, y que •stas podrlan ser acentuadas por la falta de territorialidad exhibida por la mayorla de las especies. Los tamafios poblacionales menores e correlacionaron con una competencia por interferencia reducida entre individuos. Las fluctuaciones poblacionales podrlan incrementar la habilidad de la especie subordinada R. melanosticta p ra coexistir en el bosque del plano de inundaci6n con P. nigromaculata, que es mils grande y dominante. La selecci6n de sitios de nidificaci6n podrla contribuir a la arnplitud del nicho entre las aves seguidoras de hormigas. Aqui proveo descripciones de los nidos, huevos y pichones de P. nigromaculata, R. melanosticta y G. salvini, los cuales no habian sido descritos al comienzo de este estudio.