Interregional Breeding Dispersal of Adult Roseate Terns

Braby²,

et al. 2012

J Ornithol

Understanding the spatial dynamics of populations is essential for conservation of species at the landscape level. Species that have adapted to stable environments may not move from their breeding areas even if these have become sub-optimal due to anthropogenic disturbances. Instead, they may breed unsuccessfully or choose not to breed at all. Damara Terns Sternula balaenarum feed off the highly productive Benguela Upwelling System. They breed on the coastal desert mainland of Namibia where development and off-road driving is threatening breeding areas. We report annual survival and breeding dispersal probabilities of 214 breeding adult Damara Terns through capture-mark-recapture at two colonies for 9 years (2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009) in central Namibia. Using multi-state models in program MARK, model selection based on AICc favoured a model that suggests local annual survival of Damara Terns for the dataset was 0.88 (95% CI, 0.73-0.96) and the annual dispersal probability was 0.06 (0.03-0.12). High survival and low dispersal probabilities are consistent with other seabirds adapted to stable environments. These estimates contribute to the first baseline demographic information for the Damara Tern. Low dispersal probabilities indicate that current protection of breeding sites is an important management approach for protecting the species. ZusammenfassungJährliche Ü berlebensrate und Brutortstreuung bei einem an stabile Umweltbedingungen angepassten Seevogel: Auswirkung auf Schutzmaßnahmen Um Arten auf Landschaftsebene zu schützen ist es wichtig, die räumliche Dynamik der Populationen zu verstehen. Es ist möglich, dass Arten, die an eine stabile Umwelt angepasst sind, ihre Brutgebiete nicht verändern können, selbst wenn diese infolge anthropogener Veränderungen nicht mehr optimal sind. Stattdessen könnten sie dort erfolglos zu brüten versuchen oder gar nicht mehr brüten. Damara-Seeschwalben S. balaenarum ernähren sich im hochproduktiven Benguela Auftriebsgebiet. Sie brüten an der Küste der Namibwüste, wo Ü berbauungen und Fahren im Gelände ihre Brutgebiete gefährdet. Wir präsentieren jährliche Ü berlebensraten und Dispersionswahrscheinlichkeiten basierend auf 214 brütenden adulten Damara-Seeschwalben, ermittelt durch Fang-Wiederfang Methoden über neun Jahre Modelle in Programm MARK zeigten für diese Daten, dass die jährliche lokale Ü berlebensrate von Damara-Seeschwalben 0.88 (95% Vertrauernsbereich 0.73-0.96) war und die jährliche Dispersionswahrscheinlichkeit zwischen den Kolonien betrug 0.06 (0.03-0.12). Die hohe Ü berlebensrate und niedrige Dispersionswahrscheinlichkeit sind vergleichbar mit anderen an stabile Umwelten angepassten Seevö-geln. Diese Schätzungen sind ein erster Beitrag zum Verständnis der Demographie von Damara-Seeschwalben. Die niedere Dispersionswahrscheinlichkeiten legen nahe, dass der Schutz der Brutgebiete, wie er momentan betrieben wird, eine tatsächlich wichtige Maßnahme zum Schutz dieser Art ist.

Section: Discussionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Annual survival and breeding dispersal of a seabird adapted to a stable environment: implications for conservation

Braby²,

et al. 2012

J Ornithol

“…Birds from this cohort that survived and returned to the breeding area were sampled in a recapture and resighting programme described by Spendelow et al (2008). This programme systematically sampled breeding Roseate Terns at the five major breeding sites in the Northwest Atlantic metapopulation, and non-breeding birds at four of these sites; less systematic resighting programmes were carried out at many of the minor breeding sites (Spendelow et al 2010), so the entire metapopulation was sampled. Birds from our cohort were encountered from 1999 to 2009 (see Supporting Online Information, Table S1); the recapture/resighting programme was scaled back after 2009.…”

Section: Study Site and Study Cohortmentioning

confidence: 99%

Prebreeding survival of Roseate Terns Sterna dougallii varies with sex, hatching order and hatching date

Nisbet¹,

Monticelli

Spendelow³

et al. 2016

Ibis

Self Cite

Unequal sex ratios can reduce the productivity of animal populations and are especially prevalent among endangered species. A cohort of 333 Roseate Tern Sterna dougallii chicks at a site where the adult sex ratio was skewed towards females was sexed at hatching and followed through fledging and return to the breeding area, and subsequently during adulthood. The entire regional metapopulation was sampled for returning birds. Prebreeding survival (from fledging to age 3 years) was lower in males than in females, but only among B‐chicks (second in hatching order). Prebreeding survival also declined with hatching date. The proportion of females in this cohort increased from 54.6% at hatching to 56.2% at fledging and to an estimated 58.0% among survivors at age 3 years. This was more than sufficient to explain the degree of skew in the sex ratio of the adult population, but changes in this degree of skew during the study period make it difficult to identify the influence of a single cohort of recruits. Many studies of prebreeding survival in other bird species have identified effects of sex, hatching order or hatching date, but no previous study has tested for effects of all three factors simultaneously.

“…Breeding site fidelity is usually high (around 90 %), but depends on the site, predation rate, disturbance and distance to other colonies (Spendelow et al 1995;Lebreton et al 2003;Devlin et al 2008, Braby et al 2012. Cases of distant breeding dispersal (200-400 km) have also been reported (Spendelow et al 2010). As in most birds, natal dispersal among terns occurs with a greater probability than breeding dispersal (Greenwood and Harvey 1982;Spendelow 1991;Lebreton et al 2003).…”

Section: Introductionmentioning

confidence: 99%

Adult and pre-breeding survival estimates of the Whiskered Tern Chlidonias hybrida breeding in southern Poland

Ledwoń

Neubauer

Betleja³

2013

J Ornithol

We present the first-ever survival estimates of the Whiskered Tern Chlidonias hybrida, based on the analysis of capture-recapture data (403 adults and 1,484 chicks ringed) collected between 1993 and 2011 in an increasing breeding population in southern Poland. Data were modelled using multistate models with an unobservable state, accounting for the period during which young terns remain at their winter quarters. Model-averaged prebreeding and breeding survival were estimated to be 0.54 [standard error (SE) 0.28] and 0.80 (SE = 0.05), respectively. All models were in agreement that the relative proportion of breeders was nearly zero in the second calendar year, increasing to reach values close to 0.8 in the fifth calendar year, which confirms the observation of a much delayed maturation of the Whiskered Tern. Our data indicate that most Whiskered Tern start to breed about 1 year earlier than members of genera Sterna and Onychoprion. However, the precision of the estimates for the parameter describing the transition probability from the unobservable pre-breeding to the observable breeding state was extremely poor; therefore, these estimates should be treated as tentative until more data are collected. The three best-supported models indicated significant annual variation in recapture probability. The results also suggested that forced exchange of breeding colonies is frequent in the study area; consequently, a large proportion of birds ringed as chicks are breeding in colonies other than their respective natal colony. This exchange is best explained not by the trapping and ringing activity but by human management of the environment, such as water level changes in dam reservoirs and carp Cyprinus carpio farming at fish ponds, both of which result in breeding habitats becoming unstable and periodically unavailable, possibly forcing birds to change breeding sites.Keywords Whiskered Tern Á Chlidonias hybrida Á Capture-mark-recapture modelling Á Apparent survival Á Age at first breeding Á Fidelity Á Bird trapping