Initiation Distance (initiation + distance)

Distribution by Scientific Domains

Kinds of Initiation Distance

  • flight initiation distance


  • Selected Abstracts


    Behavioral responses of nesting birds to human disturbance along recreational trails

    JOURNAL OF FIELD ORNITHOLOGY, Issue 2 2010
    Jennifer R. Smith-Castro
    ABSTRACT The presence of recreational trails can impact breeding birds either indirectly by altering habitat or the movement patterns of predators or directly if the presence of humans disturbs birds. We examined the behavioral responses of nesting female Northern Cardinals (Cardinalis cardinalis) to human disturbance using both experimental and observational approaches. From April to August 2006 and 2007, we monitored Northern Cardinal nests in 18 riparian forests in Ohio, USA. Two experimental trials were conducted at each nest (N= 63), with Flight Initiation Distance (FID, the distance at which a bird flushed from the nest) recorded as we approached nests by walking directly toward them and by walking along trails located variable distances from nests. We also measured flight initiation distance (FID) when nests were approached during routine nest checks (N= 160). Cardinals were six times more likely to flush when nests were approached directly, and females on higher nests were less likely to flush regardless of distance to trail. FID was not significantly influenced by the distance of nests from trails. We found no association between nest survival and the tendency of birds to flush. Rather, nest survival was best explained by nest height. Thus, our findings suggest that the responses of birds to human use of recreational trails have only short-term effects, with no apparent effects of on nest survival. Because the reaction of birds to humans in our study depended on how nests were approached, studies where FID is used as an indicator of sensitivity to human disturbance and is determined by direct approaches may overestimate the potential impact of trails on nesting birds. RESUMEN Los senderos recreativos pueden tener impactos indirectos a las aves reproductoras por la modificación del hábitat o por la alteración de los patrones de movimiento de los depredadores y tambien pueden tener impactos directos por la perturbación de las actividades humanas. Las respuestas del comportamiento de las hembras de la especie Cardinalis cardinalis a la perturbación humana fueron estudiados usando métodos experimentales y observacionales que aplicaron la Distancia del Comienzo de Vuelo (FID por sus siglas en inglés) como una medida de sensibilidad. De Abril , Agosto de los años 2006 y 2007, monitoreamos nidos de Cardinalis cardinalis en 18 sitios de bosque ripario en Ohio, EEUU. Realizamos dos pruebas experimentales para cada nido (N= 63), así que se registró FID para cada nido cuando se hizo un acercamiento al nido o directamente o por el sendero. Adicionalmente, recopilamos la FID para los acercamientos directos durante los chequeos rutinarios de los nidos (N= 160). Era seis veces mas probable que las aves volarían cuando se hizo el acercamiento al nido directamente, que cuando un observador pas' por el sendero. Era menos probable que las aves volarían de los nidos altos, pero la tendencia de volar no era relacionada a la distancia al sendero. La FID no estaba relacionada significativamente a la distancia al sendero ni a la altura del nido. No encontramos ninguna asociación entre sobrevivencia del nido y la tendencia de volar; sino la mejor explicación para el éxito de la anidación fue solo la altura del nido. Por lo tanto, estos resultados sugieren que las respuestas del comportamiento de las aves al uso recreativo de los senderos representan efectos de corto plazo y con pocas consecuencias importantes a la reproducción. Como la reaccion de las aves a los humanos dependia de la manera en que se hicieron los acercamientos, los estudios que utilizan la respuesta de la FID a los acercamientos directos como un indicador de sensibilidad a la perturbación humana podrían sobreestimar los impactos potenciales de los senderos en los nidos. [source]


    Plesiomorphic Escape Decisions in Cryptic Horned Lizards (Phrynosoma) Having Highly Derived Antipredatory Defenses

    ETHOLOGY, Issue 10 2010
    William E. Cooper Jr
    Escape theory predicts that the probability of fleeing and flight initiation distance (predator,prey distance when escape begins) increase as predation risk increases and decrease as escape cost increases. These factors may apply even to highly cryptic species that sometimes must flee. Horned lizards (Phrynosoma) rely on crypsis because of coloration, flattened body form, and lateral fringe scales that reduce detectability. At close range they sometimes squirt blood-containing noxious substances and defend themselves with cranial spines. These antipredatory traits are highly derived, but little is known about the escape behavior of horned lizards. Of particular interest is whether their escape decisions bear the same relationships to predation risk and opportunity costs of escaping as in typical prey lacking such derived defenses. We investigated the effects of repeated attack and direction of predator turning on P. cornutum and of opportunity cost of fleeing during a social encounter in P. modestum. Flight initiation distance was greater for the second of two successive approaches and probability of fleeing decreased as distance between the turning predator and prey increased, but was greater when the predator turned toward than away from a lizard. Flight initiation distance was shorter during social encounters than when lizards were solitary. For all variables studied, risk assessment by horned lizards conforms to the predictions of escape theory and is similar to that in other prey despite their specialized defenses. Our findings show that these specialized, derived defenses coexist with a taxonomically widespread, plesiomorphic method of making escape decisions. They suggest that escape theory based on costs and benefits, as intended, applies very generally, even to highly cryptic prey that have specialized defense mechanisms. [source]


    Risk Assessment and Withdrawal Behavior by Two Species of Aposematic Poison Frogs, Dendrobates auratus and Oophaga pumilio, on Forest Trails

    ETHOLOGY, Issue 4 2009
    William E. Cooper Jr
    Many chemically defended prey advertize toxicity to predators by aposematic coloration. When aposematic prey are approached, they often move slowly or not at all, allowing predators to evaluate their unprofitability. Poison frogs (Dendrobatidae) are toxic, aposematically colored, forage openly and diurnally, and are much easier to capture than many palatable frogs. Although protected against diverse predators, they are sometimes attacked and are subjected to injury by large animals without predatory intent. We predicted that they have limited escape behavior, but retain ability to assess and respond to risk. When we approached Dendrobates auratus and Oophaga pumilio on forest trails, both species hopped by the shortest route to the nearer forest edge and stopped there. When approached, D. auratus moved after shorter latency at an angle closer to perpendicular to the forest edge, were more likely to leave the trail, and left the trail sooner with fewer changes in direction after moving a shorter distance than when not approached. In agreement with predictions of optimal escape theory based on risk, flight initiation distance by D. auratus was greater when approached directly than indirectly and rapidly than slowly, and was greater when frogs were in the open than partially concealed. Frogs neither attempted rapid escape nor entered refuges. Both species hopped leisurely and remained visible after stopping. They exhibit the diminished escape behavior of aposematic prey, yet retain the capacity to assess risk and adjust behavior accordingly. Their behavior demonstrates continued need for escape behavior by highly toxic aposematic prey. [source]


    Avian Risk Assessment: Effects of Perching Height and Detectability

    ETHOLOGY, Issue 4 2004
    Daniel T. Blumstein
    We studied two components of predator risk assessment in birds. While many species are limited to seeking safety under cover or under ground, some birds can fly away from their predators and escape to trees. If birds in fact ,feel' safer (e.g. perceive less risk) in trees, we would expect them to tolerate closer approach by a potential terrestrial predator. Another component of safety is at which point the animal detects an approaching threat, which we expected to increase with eye size, assuming eye size is a surrogate for visual acuity. We used the distance birds moved away from an approaching human [flight initiation distance (FID)] as a metric to determine whether birds associated a lower risk of predation by being in trees, and we used the distance at which birds first displayed alert behaviors from an approaching human (alert distance) to determine if birds with larger eyes had higher detection distances. Although some species were affected by tree height, we found no clear pattern that birds assessed themselves to be at a lower risk of predation when they were ,3 m above the ground compared with being <3 m above ground. In the 10 species for which height had any significant effect on FID, birds ,3 m off the ground had greater FIDs in six species, but the remaining three species had the opposite response. While we found a significant positive relationship between eye size and alert distance in 23 species, the relationship was not present in a phylogenetic analysis using independent contrasts, which suggests that the apparent relationship was influenced strongly by the association between the studied species. Together, these results suggest that birds do not obviously associate being in a tree with safety, and that variations in visual acuity, per se, cannot be used as a general indicator of differences in alert distances, as previously suggested in the literature. [source]


    Up, up, and away: relative importance of horizontal and vertical escape from predators for survival and senescence

    JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 8 2010
    A. P. MØLLER
    Abstract Animals fleeing a potential predator can escape horizontally or vertically, although vertical flight is more expensive than horizontal flight. The ability to escape in three dimensions by flying animals has been hypothesized to result in greater survival and eventually slower senescence than in animals only fleeing in two dimensions. In a comparative study of flight initiation distance in 69 species of birds when approached by a human, I found that the amount of variance explained by flight initiation distance was more than four times as large for the horizontal than the vertical component of perch height when taking flight. The slope of the relationship between horizontal distance and flight initiation distance (horizontal slope) increased with increasing body mass across species, whereas the slope of the relationship between vertical distance and flight initiation distance (vertical slope) decreased with increasing body mass. Therefore, there was a negative relationship between horizontal and vertical slope, although this negative relationship was significantly less steep than expected for a perfect trade-off. The horizontal slope decreased with increasing density of the habitat from grassland over shrub to forest, whereas that was not the case for the vertical slope. Adult survival rate increased and rate of senescence (longevity adjusted for survival rate, body mass and sampling effort) decreased with increasing vertical, but not with horizontal slope, consistent with the prediction that vertical escape indeed provides a means of reducing the impact of predation. [source]


    Behavioral responses of nesting birds to human disturbance along recreational trails

    JOURNAL OF FIELD ORNITHOLOGY, Issue 2 2010
    Jennifer R. Smith-Castro
    ABSTRACT The presence of recreational trails can impact breeding birds either indirectly by altering habitat or the movement patterns of predators or directly if the presence of humans disturbs birds. We examined the behavioral responses of nesting female Northern Cardinals (Cardinalis cardinalis) to human disturbance using both experimental and observational approaches. From April to August 2006 and 2007, we monitored Northern Cardinal nests in 18 riparian forests in Ohio, USA. Two experimental trials were conducted at each nest (N= 63), with Flight Initiation Distance (FID, the distance at which a bird flushed from the nest) recorded as we approached nests by walking directly toward them and by walking along trails located variable distances from nests. We also measured flight initiation distance (FID) when nests were approached during routine nest checks (N= 160). Cardinals were six times more likely to flush when nests were approached directly, and females on higher nests were less likely to flush regardless of distance to trail. FID was not significantly influenced by the distance of nests from trails. We found no association between nest survival and the tendency of birds to flush. Rather, nest survival was best explained by nest height. Thus, our findings suggest that the responses of birds to human use of recreational trails have only short-term effects, with no apparent effects of on nest survival. Because the reaction of birds to humans in our study depended on how nests were approached, studies where FID is used as an indicator of sensitivity to human disturbance and is determined by direct approaches may overestimate the potential impact of trails on nesting birds. RESUMEN Los senderos recreativos pueden tener impactos indirectos a las aves reproductoras por la modificación del hábitat o por la alteración de los patrones de movimiento de los depredadores y tambien pueden tener impactos directos por la perturbación de las actividades humanas. Las respuestas del comportamiento de las hembras de la especie Cardinalis cardinalis a la perturbación humana fueron estudiados usando métodos experimentales y observacionales que aplicaron la Distancia del Comienzo de Vuelo (FID por sus siglas en inglés) como una medida de sensibilidad. De Abril , Agosto de los años 2006 y 2007, monitoreamos nidos de Cardinalis cardinalis en 18 sitios de bosque ripario en Ohio, EEUU. Realizamos dos pruebas experimentales para cada nido (N= 63), así que se registró FID para cada nido cuando se hizo un acercamiento al nido o directamente o por el sendero. Adicionalmente, recopilamos la FID para los acercamientos directos durante los chequeos rutinarios de los nidos (N= 160). Era seis veces mas probable que las aves volarían cuando se hizo el acercamiento al nido directamente, que cuando un observador pas' por el sendero. Era menos probable que las aves volarían de los nidos altos, pero la tendencia de volar no era relacionada a la distancia al sendero. La FID no estaba relacionada significativamente a la distancia al sendero ni a la altura del nido. No encontramos ninguna asociación entre sobrevivencia del nido y la tendencia de volar; sino la mejor explicación para el éxito de la anidación fue solo la altura del nido. Por lo tanto, estos resultados sugieren que las respuestas del comportamiento de las aves al uso recreativo de los senderos representan efectos de corto plazo y con pocas consecuencias importantes a la reproducción. Como la reaccion de las aves a los humanos dependia de la manera en que se hicieron los acercamientos, los estudios que utilizan la respuesta de la FID a los acercamientos directos como un indicador de sensibilidad a la perturbación humana podrían sobreestimar los impactos potenciales de los senderos en los nidos. [source]