Growth of Brown Pelican Nestlings Exposed to Sublethal Levels of Soft Tick Infestation

Abstract

Ectoparasites are a common component of seabird colonies and are generally considered to have a negative impact on their hosts. Nest parasites such as the soft tick Carios capensis may pose a distinct threat to altricial nestlings confined to the nest and unable to escape infestation. To assess the potential effects of ticks on growth, we measured linear growth rates of Brown Pelican (Pelecanus occidentalis) nestlings during early development in relation to C. capensis infestation at insecticide treated and untreated nests at two colonies in South Carolina during the 2004 and 2005 breeding seasons. Tick infestation levels differed between colonies but not between years. We found a positive relationship between tick infestation and both growth rates and hatching success at the more infested colony. We did not find a consistent relationship between insecticide treatment and growth rates, although chicks from nests treated with insecticide had fewer ticks compared to chicks from untreated nests. Our study suggests that the cohabitation of ectoparasites and seabirds within colonies may result in behavioral or physiological adaptations of adults or nestlings that inhibit the expected negative effect of ectoparasites on nestling growth at sublethal levels of infestation.Resumen. Los ectoparásitos son un componente común de las colonias de aves marinas y generalmente se considera que tienen un impacto negativo sobre sus hospederos. Los parásitos de nido como la garrapata Carios capensis pueden resultar una amenaza particular para los pichones nidícolas confinados al nido e incapaces de escapar de la infestación. Para evaluar los efectos potenciales de las garrapatas sobre el crecimiento, medimos las tasas lineales de crecimiento de los pichones de Pelecanus occidentales durante el desarrollo temprano con relación a la infestación de C. capensis en nidos tratados y no tratados con insecticida, en dos colonias en Carolina del Sur durante las estaciones reproductivas del 2004 y 2005. Los niveles de infestación de garrapatas difirieron entre las colonias pero no entre los años. Encontramos una relación positiva entre la infestación de garrapatas tanto con las tasas de crecimiento como con eléxito de eclosión en la colonia más infestada. No encontramos una relación consistente entre el tratamiento con insecticida y las tasas de crecimiento, aunque los pichones de los nidos tratados con insecticida tuvieron menos garrapatas que los pichones de los nidos no tratados. Nuestro estudio sugiere que la convivencia de los ectoparásitos con las aves marinas en las colonias puede causar adaptaciones de comportamiento o fisiológicas de los adultos o de los pichones que inhiben el efecto negativo esperado de los ectoparásitos sobre el crecimiento de los pichones a niveles subletales de infestación.

Negative effects of yolk testosterone and ticks on growth in canaries

“…1 and 2) (e.g. Young, '93; Merino and Potti, '95; Dufva and Allander, '96), but contrasts with the effects reported in two previous studies (Eggert and Jodice, 2008; Gallizzi et al, 2008). But Gallizzi et al (2008) infested chicks with tick larvae, which suck less blood than tick nymphs (Balashov, '72; Hillyard, '96), while Eggert and Jodice (2008) used a naturally occurring tick infestation.…”

“…Young, '93; Merino and Potti, '95; Dufva and Allander, '96), but contrasts with the effects reported in two previous studies (Eggert and Jodice, 2008; Gallizzi et al, 2008). But Gallizzi et al (2008) infested chicks with tick larvae, which suck less blood than tick nymphs (Balashov, '72; Hillyard, '96), while Eggert and Jodice (2008) used a naturally occurring tick infestation. It should be noted that ticks are no common ectoparasites in domesticated canaries, and domesticated canaries may thus have weaker defence mechanisms against this type of parasite.…”

Physical condition and stress levels during early development reflect feeding rates and predict pre- and post-fledging survival in a nearshore seabird

“…If multiple nestlings were present, we sampled all siblings and determined hatch order based on culmen length (i.e. culmen length was assumed to be greater in first-hatched than second-hatched chicks, and in second-hatched than third-hatched chicks; Eggert and Jodice, 2008). Nestlings were readily captured by hand at or near nest sites.…”

A review of available methods and description of a new method for eliminating ectoparasites from bird nests

“…Tetrachlorovinphos has been used to reduce numbers of soft ticks ( Ornithodoros capensis ) in nests of Brown Pelicans ( Pelecanus occidentalis ) (Norcross and Bolen , Eggert and Jodice , Eggert et al. 2010).…”