Declines in reproductive performance among older age classes have been reported in many bird and mammal species, and are commonly presented as demonstrating reproductive senescence. However, no ...declines in performance could be demonstrated in studies of several bird species. We measured reproductive performance in Common Terns (Sterna hirundo) of known age (2–28 yr) during a 19-yr period at a site in Buzzards Bay, Massachusetts, USA. We measured 6 components of reproductive performance and used generalized additive mixed models (GAMMs) in a Bayesian framework to analyze dependence of each measure on parental age, while controlling for variations among years and indices of individual quality. Four measures of performance improved (earlier laying date, higher values of clutch size, fledging success, and productivity) with age, most rapidly between ages 2 and 10 yr; egg mass and hatching success varied only slightly with age. No measure of performance showed reversals among the older age classes; fledging success and productivity continued to increase through at least age 22 yr. These findings are consistent with results from an earlier study of the same species. Continued increase in reproductive performance through the oldest age classes is not incompatible with “reproductive senescence” (decline in physiological or other functions required for successful reproduction) if either reproductive effort or efficiency continue to increase. Studies within our population have yielded no evidence for age-related increase in reproductive effort, but 3 studies have suggested that older Common Terns can raise chicks more successfully than younger birds without increasing reproductive effort, probably by more efficient foraging and chick provisioning. Our findings suggest that Common Terns offset reproductive senescence by continuing to improve efficiency through at least age 22 yr. Age-related changes in efficiency should be investigated in other species with similar life-history traits. LAY SUMMARY We studied Common Terns (Sterna hirundo) at a breeding colony in Massachusetts from 1970 until 2003: we banded chicks when they hatched so that we could determine their age when they returned to breed at the same site in subsequent years. The terns' breeding success continued to improve with age throughout their lives and was still increasing among birds that were 22 years old. Common Terns continually improve their skills at finding fish and provisioning their chicks, even after 20 years of practice.
Post‐natal growth is an important life‐history trait and can be a sensitive indicator of ecological stress. For over 50 years, monotonic (never‐decreasing) growth has been viewed as the predominant ...trajectory of post‐natal mass change in most animal species, notably among birds. However, prevailing analytical approaches and energetic constraints may limit detection of non‐monotonic (or multiphasic), determinate growth patterns, such as mass recession in birds (weight loss prior to fledging, preceded by overshooting adult mass), which is currently believed to be restricted to few taxa. Energetic surplus and shortfall are widespread conditions that can directly influence the degree of mass overshooting and recession. Thus, we hypothesize that in many species, prevailing energetic constraints force mass change away from a fundamental non‐monotonic trajectory to instead follow a monotonic curve. We observed highly non‐monotonic, mass change trajectories (overshooting adult mass by up to almost 20%) among common tern Sterna hirundo chicks, a well‐studied species long‐established as growing monotonically. We quantified the prevalence and magnitude of non‐monotonic mass change prior to fledging for 313 common tern chicks that successfully fledged from two discrete populations in multiple years. We used a new approach for analysing non‐monotonic curves to examine differences in mass change trajectories between populations under contrasting abiotic (freshwater vs. saltwater) and biotic stresses (low rates of food provisioning). Some degree of mass recession occurred in 73% of all study chicks. Overshooting adult mass followed by extensive mass recession was most prevalent at our freshwater colony, being detected among 34–38% of chicks annually. Non‐monotonic trajectories were less marked in populations experiencing ecological stress and among lower quality individuals. Chicks that were provisioned at higher rates were more likely to both overshoot adult mass and experience subsequent mass recession. Our results in common terns provide strong support for the hypothesis that non‐monotonic trajectories are the fundamental pattern of mass change but are constrained to be monotonic under energetic shortfall. This justifies future tests of the generality of this hypothesis across a broad range of taxa. We also demonstrate a recent analytical tool that prevents routine fitting of monotonic curves without prior investigation of non‐monotonic trends.
Common Terns Sterna hirundo and Roseate Terns S. dougallii rarely rest on the sea surface during the breeding season but frequently do so in winter and on migration.
To investigate the behaviour of ...Common and Roseate Terns throughout the annual cycle using immersion sensors.
We analyzed data from immersion sensors attached to 11 Common Terns and 6 Roseate Terns that bred in the northeastern USA and wintered either on the north or east coasts of South America, to investigate temporal patterns of resting on saltwater throughout the annual cycle.
Both species of tern rarely contacted salt water during the breeding season, except when bathing or plunge-diving, but in winter they spent several hours each day resting on the sea surface. This resting was most frequent around midday and least frequent in early mornings and late afternoons. Night-time immersion varied widely among individuals but terns wintering in eastern Brazil were less likely to spend the night on the sea surface than those wintering on the north coast of South America. We suggest that this reflected the availability of dry-land roosting sites.
Our results are consistent with and extend studies from Europe, confirming that although Common and Roseate Terns spend very little time resting on the sea surface in the breeding season, this behaviour is frequent during migration and wintering periods.
The rate of telomere loss is related to maximum lifespan in birds Tricola, Gianna M.; Simons, Mirre J. P.; Atema, Els ...
Philosophical transactions of the Royal Society of London. Series B. Biological sciences,
03/2018, Letnik:
373, Številka:
1741
Journal Article
Recenzirano
Odprti dostop
Telomeres are highly conserved regions of DNA that protect the ends of linear chromosomes. The loss of telomeres can signal an irreversible change to a cell's state, including cellular senescence. ...Senescent cells no longer divide and can damage nearby healthy cells, thus potentially placing them at the crossroads of cancer and ageing. While the epidemiology, cellular and molecular biology of telomeres are well studied, a newer field exploring telomere biology in the context of ecology and evolution is just emerging. With work to date focusing on how telomere shortening relates to individual mortality, less is known about how telomeres relate to ageing rates across species. Here, we investigated telomere length in cross-sectional samples from 19 bird species to determine how rates of telomere loss relate to interspecific variation in maximum lifespan. We found that bird species with longer lifespans lose fewer telomeric repeats each year compared with species with shorter lifespans. In addition, phylogenetic analysis revealed that the rate of telomere loss is evolutionarily conserved within bird families. This suggests that the physiological causes of telomere shortening, or the ability to maintain telomeres, are features that may be responsible for, or co-evolved with, different lifespans observed across species.
This article is part of the theme issue ‘Understanding diversity in telomere dynamics'.
We measured breeding performance of little penguins Eudyptula minor at Phillip Island, Victoria, Australia, during a 21-year period. All birds considered in this paper (n=307) were of known age (2-22 ...y) and sex, and most were of known, or closely-estimated, pair-bond status (1-8 mates per bird; pair-bond durations 1-13 y). Breeding dates and breeding performance varied markedly from year to year; measures of annual performance were not associated with early breeding. Measures of individual breeding performance (clutch-size, hatching success, chick masses and productivity) were related to early laying, parental age, and duration of pair-bond. Dependence of breeding performance on parental age was curvilinear, levelling off at about 8 y of age. Productivity declined significantly among birds older than 8 y; this decline was not due to events in the last year of breeding ("terminal illness"). Breeding performance increased with duration of pair-bond at least through y 5. Early breeding was significantly related to age and duration of pair-bond. Most of these relationships were stronger among males than among females, and many of them were not significant when females were considered alone. After controlling for other factors, breeding performance varied significantly among birds, but autocorrelations were low and limited to intervals of one year. Parental quality (defined for birds studied in six or more years as the individual bird term in a GLM for productivity controlling for other factors) was not correlated with lifespan or other demographic parameters, but high-quality birds were less prone to change mates and burrows than low-quality birds. We know of no previous study in which simultaneous effects of laying date, age and pair-bond duration on breeding performance were measured, while controlling for year, individual quality and terminal illness.
Common and roseate terns are migratory piscivorous seabirds with major breeding colonies within feeding range of the polychlorinated biphenyl (PCB)-contaminated New Bedford Harbor (NBH, MA, USA) ...Superfund site. Our longitudinal study shows that before PCB discharges into NBH ceased (late 1970s), tern eggs had very high but variable PCB concentrations. However, egg concentrations of PCBs as well as DDE (1,1-bis(p-chlorophenyl)-2,2-dichloroethene), the degradation product of the ubiquitous global contaminant DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl) ethane), have since declined. Rate constants for temporal decline of PCB congeners in tern eggs varied inversely with log10 K OW (n-octanol–water partition coefficient), shifting egg congener patterns away from those characterizing NBH sediment. To estimate the toxic effects on tern eggs of PCB dioxin-like congener (DLC) exposures, we extrapolated published laboratory data on common terns to roseate terns by characterizing genetic and functional similarities in species aryl hydrocarbon receptors (AHRs), which mediate DLC sensitivity. Our assessment of contaminant risks suggests that terns breeding near NBH were exposed historically to toxic levels of PCBs and DDE; however, acute effects on tern egg development have become less likely since the 1970s. Our approach demonstrates how comparative genetics at target loci can effectively increase the range of inference for chemical risk assessments from tested to untested and untestable species.
Dispersal is increasingly recognized as a process of fundamental importance in population dynamics and other aspects of biology. Concurrently, interest in age‐dependent effects on survival, including ...actuarial senescence, has increased, especially in studies of long‐lived seabirds. Nevertheless, datasets necessary for studying dispersal and age‐dependent effects are few, as these require simultaneous data collection at two or more sites over many years. We conducted a 22‐year capture‐mark‐recapture study of Common Terns Sterna hirundo at three breeding colonies 10–26 km apart in Buzzards Bay, Massachusetts, USA. All birds in the study were of known age (range 2–28 years, median 7 years, n = 3290) and 77% were of known sex. Estimates of adult recapture, survival and breeding dispersal rates were obtained for all age‐classes from 2 to 20 years. The model that acquired 100% of the QAICc (Akaike's Information Criterion adjusted for small sample size and overdispersion) weight in our analysis included age‐specificity in all parameters but no relationship with sex. Our study may be the first to demonstrate age‐specificity in recapture, survival and breeding dispersal rates simultaneously, using a single model. Annual rates of breeding dispersal ranged from <0.01 to 0.27, with a population‐weighted mean of 0.065; they decreased with increasing distance between colony sites and, unexpectedly, increased with age. Breeding dispersal did not increase consistently after years with predation on adults or after an attempt to displace birds from an oiled site. Survival rates did not vary among sites or years. Annual adult survival increased from 0.80 in 2‐year‐old birds to a maximum of approximately 0.88 around age 8 years and then declined to 0.76 at age 20 years, yielding strong evidence for actuarial senescence. The peak annual survival rate of 0.88 is at the low end of other estimates for Common Tern and in the lower part of the range recorded for other terns, but total numbers in the three colonies increased seven‐fold during the study. This was part of a slower increase in the regional population, with net immigration into the study colonies. Our results demonstrate the biological significance of breeding dispersal in local population dynamics and age‐related effects on survival and dispersal from a metapopulation of a long‐lived seabird.
'Immuno-oncology' is the current buzzword in cancer treatment, with drugs like pembrolizumab (KEYTRUDA) and nivolumab (Opdivo) providing exciting new treatment options for an expanding range of ...tumour types, including melanoma and lung cancer. The ability to activate the immune system to kill cancer cells has become a focus area for oncology drug discovery and development.
•A model on the dynamics of a fragmented population of a bird species is proposed.•Understanding seabird dynamics is inhibited by limited data on colonization events.•Large colony population size ...exhibits a threshold sensitivity to adult survival.•Model results suggest that regional persistence is maintained by large populations.
The endangered population of roseate terns (Sterna dougallii) in the Northwestern Atlantic Ocean consists of a network of large and small breeding colonies on islands. This type of fragmented population poses an exceptional opportunity to investigate dispersal, a mechanism that is fundamental in population dynamics and is crucial to understand the spatio-temporal and genetic structure of animal populations. Dispersal is difficult to study because it requires concurrent data compilation at multiple sites. Models of population dynamics in birds that focus on dispersal and include a large number of breeding sites are rare in literature. In this work, we propose a stochastic simulation model that captures the dispersal dynamics of this population of roseate terns. The colonization and decolonization (abandonment) of breeding colonies are modeled as discrete events that follow different dynamics than dispersal. We show that our model reproduces the properties of this population that have been observed in field data. We also analyzed the sensitivity of our model to alterations in different variables, and study the impact of these alterations in the model dynamics. Our results suggest that large colony population size exhibits a threshold sensitivity to adult survival, and that regional persistence is maintained by the larger populations.
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