Survival of postfledging Forster’s terns in relation to mercury exposure in San Francisco Bay

Ackerman, Joshua T.; Eagles‐Smith, Collin A.; Takekawa, John Y.; Iverson, Samuel A.

doi:10.1007/s10646-008-0237-6

Cited by 22 publications

(20 citation statements)

References 64 publications

(84 reference statements)

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“…Although Forster's tern chick survival to fledging was higher than that of American avocet chicks ( Recurvirostra americana ; 0.06), it was much lower than those of black‐necked stilt chicks ( Himantopus mexicanus ; 0.40) studied at similar sites in San Francisco Bay in 2005 and 2006 (Ackerman et al ). Once fledged, Forster's tern cumulative survival rate during the subsequent 35‐day postfledging time period was 0.81 in San Francisco Bay (Ackerman et al ). Combining these data for postfledging survival (Ackerman et al ) with our current study's estimate for overall tern chick survival from hatch to fledging (0.22), provides an estimated Forster's tern chick survival from hatch to 35‐days postfledging of 0.18 (61 total days after hatching).…”

Section: Discussionmentioning

confidence: 99%

“…Once fledged, Forster's tern cumulative survival rate during the subsequent 35‐day postfledging time period was 0.81 in San Francisco Bay (Ackerman et al ). Combining these data for postfledging survival (Ackerman et al ) with our current study's estimate for overall tern chick survival from hatch to fledging (0.22), provides an estimated Forster's tern chick survival from hatch to 35‐days postfledging of 0.18 (61 total days after hatching).…”

Section: Discussionmentioning

confidence: 99%

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Forster's tern chick survival in response to a managed relocation of predatory California gulls

et al. 2014

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Gull populations can severely limit the productivity of waterbirds. Relocating gull colonies may reduce their effects on nearby breeding waterbirds, but there are few examples of this management strategy. We examined gull predation and survival of Forster's tern (Sterna forsteri) chicks before (2010) and after (2011) the managed relocation of the largest California gull (Larus californicus) colony (24,000 adults) in San Francisco Bay, California. Overall, survival of radio‐marked Forster's tern chicks from hatching to fledging was 0.22 ± 0.03 (mean ± SE), and daily survival rates increased with age. Gulls were the predominant predator of tern chicks, potentially causing 54% of chick deaths. Prior to the gull colony relocation, 56% of radio‐marked and 20% of banded tern chicks from the nearest tern colony were recovered dead in the gull colony, compared to only 15% of radio‐marked and 4% of banded chicks recovered dead from all other tern colonies. The managed relocation of the gull colony substantially increased tern chick survival (by 900%) in the nearby (<1 km) colony from 0.04 ± 0.02 in 2010 to 0.40 ± 0.12 in 2011 but not at the more distant (>3.8 km) reference tern colony (0.29 ± 0.10 in 2010 and 0.25 ± 0.09 in 2011). Among 19 tern nesting islands, fledging success was higher when gull abundance was lower at nearby colonies and when gull colonies were farther from the tern colony. Our results indicate that the managed relocation of gull colonies away from preferred nesting areas of sensitive waterbirds can improve local reproductive success, but this conservation strategy may shift gull predation pressure to other areas or species. © 2014. This article is a U.S. Government work and is in the public domain in the USA.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Forster's tern chick survival in response to a managed relocation of predatory California gulls

et al. 2014

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“…To our knowledge, no study has yet been able to demonstrate an unambiguous link between contamination level and subsequent survival in free-living birds (see Thompson et al 1991;Meyer et al 1998;Ackerman et al 2008;Mitro et al 2008). This raises the interesting possibility that survival rates in general may be less sensitive to mercury exposure than a number of other commonly measured biological indices, such as reproductive success or immunocompetence.…”

Section: Discussionmentioning

confidence: 99%

Mercury exposure and survival in free-living tree swallows (Tachycineta bicolor)

et al. 2010

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Mercury has become a ubiquitous contaminant in food chains worldwide. A large body of literature detailing bioaccumulation and effects on birds has revealed the potential for mercury to adversely impact avian physiology and reproduction. However, the extent to which these effects impair survival remains poorly understood. The objective of this study was to determine whether mercury exposure was associated with reduced annual survivorship in tree swallows (Tachycineta bicolor) breeding at a site with legacy industrial contamination. From 2005 to 2008, we captured and marked 932 adult swallows. We used Cormack-Jolly-Seber models and an information-theoretic approach to test our hypotheses that adult survival varied by sex, breeding location, and cumulative individual mercury exposure. Blood mercury was significantly elevated on contaminated sites (2005-2007 combined mean ± SE: 2.84 ± 0.09 μg/g; reference: 0.17 ± 0.01 μg/g). Model-averaged estimates of female apparent survival ranged from 0.483 to 0.488 on reference sites and 0.473 to 0.477 on contaminated sites. For males, apparent survival ranged from 0.451 to 0.457 on reference sites and 0.444 to 0.448 on contaminated sites. Thus, we observed approximately a 1% difference in survival between mercury-contaminated and reference sites. Such a small difference is unlikely to impact population viability in this short-lived species; however, some songbirds accumulate mercury to a greater degree than tree swallows and do not possess the migratory behavior that removes swallows to less contaminated areas for the majority of the year. Identifying whether such species are at risk of suffering biologically significant reductions in survival should become a focus of future research.

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“…In addition, we excluded data recorded within 6 hr after observers entered and exited the colony. We included data in our analyses only when we knew a chick to be alive and excluded data after a chick was dead (Ackerman et al, 2008b) or permanently missing from the study area for the rest of the study period (e.g., not found by the logger, truck, or aircraft searches).…”

Section: Radio-tracking Ternsmentioning

confidence: 99%

Postfledging Forster's Tern Movements, Habitat Selection, and Colony Attendance in San Francisco Bay

Ackerman

Bluso-Demers

Takekawa

2009

Condor

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Resumen. Se conoce relativamente poco a cerca de las aves durante el período posterior al emplumamiento, cuando los pichones con capacidad de volar han abandonado el nido y deben aprender a forrajear independientemente. Examinamos los movimientos posteriores al abandono del nido, la selección de hábitat y la presencia en las colonias de individuos de la especie Sterna forsteri marcados con transmisores de radio justo antes del emplumamiento en la bahía de San Francisco, California. La proporción del día que las aves jóvenes pasaron en su colonia natal disminuyó a medida que su edad aumentó, desde el 65% al momento del emplumamiento hasta menos del 5% a las dos semanas de haber emplumado. De modo concordante, la distancia a su colonia a la que las aves fueron localizadas aumentó con su edad, de menos de 500 m durante la primera semana después de abandonar el nido a más de 5000 m para la quinta semana. La hora del día también influenció la presencia en la colonia: las aves de mayor edad pasaron más tiempo en la colonia durante las horas de la noche (20:00 a 05:00) que durante el día (06:00 a 19:00), cuando presumiblemente estaban forrajeando. Los ámbitos hogareños y las áreas núcleo de uso promediaron 12.14 km 2 y 2.23 km 2 , respectivamente. A cada una de cuatro escalas espaciales de análisis, las aves mostraron una preferencia marcada por los ambientes de estanques salinos. Los otros ambientes no fueron seleccionados a ninguna escala, pero las aves consistentemente evitaron las planicies mareales y las tierras altas. Éstas también evitaron los ambientes de bahías abiertas a las dos escalas espaciales más grandes, los pantanos mareales a las dos escalas más pequeñas y los barrizales y pantanos manejados a varias escalas. Dentro de los estanques salinos, las aves se econtraron más cerca de los diques (58 m) que lo que se esperaba (107 m). Nuestros resultados indican que los pichones de S. forsteri se dispersan desde su colonia natal antes de unas pocas semanas después de abandonar el nido, que los pichones de mayor edad usan su colonia natal principalmente para descansar durante la noche y que después del emplumamiento estas aves son altamente dependientes de los estanques salinos. POSTFLEDgINg FORSTER'S TERN MOVEMENTS, HAbITAT SELECTION, AND COLONy ATTENDANCE IN SAN FRANCISCO bAy Movimientos, Selección de Hábitat y Presencia en las Colonias de Sterna forsteri Después del EmplumamientoAbstract. Relatively little is known about birds during the postfledging period when flighted chicks have left the nest and must learn to forage independently. We examined postfledging movements, habitat selection, and colony attendance of Forster's Terns (Sterna forsteri) radio-marked just before they fledged in San Francisco bay, California. The proportion of the day spent at their natal colony declined as juveniles aged, from 65% at the time of fledging to <5% within two weeks of fledging. Accordingly, the distance postfledging terns were located from their colony increased as they aged, from <500 m within the first week of fledgin...

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Survival of postfledging Forster’s terns in relation to mercury exposure in San Francisco Bay

Cited by 22 publications

References 64 publications

Forster's tern chick survival in response to a managed relocation of predatory California gulls

Forster's tern chick survival in response to a managed relocation of predatory California gulls

Mercury exposure and survival in free-living tree swallows (Tachycineta bicolor)

Postfledging Forster's Tern Movements, Habitat Selection, and Colony Attendance in San Francisco Bay

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