Geology Reports⌕ Search

Geology topics

Jeffrey A. Spendelow

Publications and source records attributed to Jeffrey A. Spendelow.

At least 19 recordsLinked to original sources
USGS2019

Begging behavior as an honest signal of need and parent-offspring association during the post-fledging dependency period

Honest signaling mechanisms can function to appropriate care to hungry offspring and avoid misdirected care of unrelated offspring. Begging, the behavior by which offspring solicit food and parental care, may be an honest signaling mechanism for need, as well as association of parents and offspring. Roseate terns (Sterna dougallii) exhibit prolonged parental care during the post-breeding staging period, offering an ideal system in which to study begging as an honest signaling mechanism. We conducted focal sampling during two pre-migratory staging seasons (2014 and 2015) at Cape Cod National Seashore, MA to determine whether post-fledging tern begging behavior was an honest signal for need and parent-offspring association. Based on honest signaling theory, we expected begging behavior to be highest during times of high perceived need, and we expected to see a decrease in begging behavior as young terns became increasingly independent of the care-giving parent. Also, we predicted that young terns would be more likely to beg at parents than non-parents. We found that young roseate terns begged at their parents more often than non-parents; however, they did not always beg at parents. Model predictions of begging probability showed a linear relationship between begging and time of day and date of season, such that begging increased with time of day and decreased with date of season, respectively. Our results provide evidence for honest parent-offspring interactions and are inconsistent with parent-offspring conflict theory but suggest that begging may play a complex role in post-fledging parent-offspring interactions.

Massachusetts↗
USGS2019

Residency, recruitment, and stopover duration of hatch-year Roseate Terns (Sterna dougallii) during the pre-migratory staging period

Avian migratory stopover and staging sites represent important energetic bottlenecks and may influence population dynamics as much as breeding or wintering periods. Roseate terns ( Sterna dougallii ) are an ideal species to examine staging demography because >70% of the entire endangered northwest Atlantic population stages at accessible locations around Cape Cod, MA before southward migration. We quantified hatch-year tern weekly residency, weekly recruitment rate into the staging population, and derived weekly staging population growth rate during two post-breeding, pre-migratory staging seasons (2014 and 2015) at Cape Cod National Seashore. We also estimated hatch-year tern staging duration at Cape Cod staging grounds. Tern residency probability at Cape Cod National Seashore during 2014 and 2015 was nearly 1 during the first weeks of the season and decreased steadily over the last four weeks to ~0.5 in the final week of the study. Recruitment rates into the staging population, representing the weekly per capita increase in hatch-year terns during the staging season, indicated that most terns arrived on the staging grounds during the first weeks of the staging season (16 July–19 August). We also identified differences in staging duration between birds from the two breeding regions. Hatch-year terns from the southernmost region spent less time staging at Cape Cod National Seashore than their northern counterparts in both 2014 and 2015. These differences may indicate alternative staging strategies for individuals originating in different regions and possibly reveal differences in conditions between these areas; for example, in the availability of ephemeral prey fish.

Massachusetts↗
USGS2018

Evaluating response distances to develop buffer zones for staging terns

Buffer zones, calculated by flight‐initiation distance (FID), are often used to reduce anthropogenic disturbances to wildlife, but FID can vary significantly across life‐history stages. We examined the behavioral effect of potential natural (gulls and shorebirds) and anthropogenic (pedestrians) disturbance sources to staging roseate ( Sterna dougallii ) and common tern ( S. hirundo ) flocks from July to September in 2014 and 2015 at Cape Cod, Massachusetts, USA. We estimated the proportion of the flock exhibiting different responses to potential disturbance sources as a function of distance, flock size, percent roseate terns, and local disturbance rates, using Bayesian zero‐and‐one inflated beta regression. The proportion of tern flocks responding to the presence of shorebirds by flying was low (0.01 ± 0.001 [SE]) and did not vary by distance or other covariates, whereas the proportion flying in response to gulls increased as distance decreased, with smaller flocks, and with flocks with a larger proportion of roseate terns being more sensitive to gull presence. Prolonged flight response rapidly increased in probability from 0.0 to as much as 1.0 as distance from pedestrians to the flock decreased from 100 m and was much more likely with smaller flocks. Pedestrian activity levels also had an effect on flock responses; those engaged in active behaviors such as jogging were more likely to cause flushing than those engaged in passive behaviors. Terns seemed to view pedestrians as more of a threat than shorebirds and gulls, even though gulls are frequent kleptoparasites of terns. Pedestrians >120 m from a tern flock generally elicited the same probability of flight response as shorebirds and gulls. We recommend managers maintain anthropogenic disturbance levels at or below the intensity of those from natural sources at sites where recreation and wildlife values are both important. Because staging tern flocks may use a variety of areas within a site, we recommend instituting a 100‐m buffer around areas potentially used by staging flocks at Cape Cod, where we studied every location roseate terns are known to use in large numbers. For other sites used by mixed‐species tern flocks, we recommend the use of our field and analytical methods to develop appropriate buffer distances that will keep pedestrians far enough away to reduce the likelihood of flight and other non‐locomotive anti‐predator behaviors. These buffer zones will also benefit other species sensitive to human activity.

Journal of Wildlife Management↗
USGS2018

Rapid departure of Roseate Terns (Sterna dougallii) following large-scale nest failure

Nest failure of most pairs of Roseate Terns (Sterna dougallii) at Falkner Island, Connecticut, in 2002-2003 (due mainly to predation by Black-crowned Night-herons [Nycticorax nycticorax]) was followed by the rapid departure of many of the failed individuals in both years. Nine failed pairs (16.7%) stayed while 40 (74.1%) of 54 unsuccessful pairs left within 2 d following nest failure in 2002, and 7 pairs (21.9%) stayed while 25 (78.1%) of 32 unsuccessful pairs left within 2 d in 2003. Individuals that departed this colony site by the end of June likely had time to prospect and renest at another colony site in the same year, and individuals that successfully renested at another colony site could have shown reduced colony-site fidelity to Falkner Island in subsequent years.

Connecticut↗
USGS2018

Post-spring migration colony-site prospecting by Roseate Terns (Sterna dougallii)

We recorded banded Roseate Terns (Sterna dougallii) and unbanded individuals mated to banded individuals in May and the first third of June in 2001 and 2002 to quantify post spring migration prospecting by this species at Falkner Island, Connecticut, USA. In 2001, more than one quarter: 34/125 (27.2%) of those observed by 19 May and 38/150 (25.3%) of those observed by 25 May did not remain at this colony site and went elsewhere to attempt breeding. In 2002, fewer terns were observed by 19 May, but an even higher percentage: 11/28 (39.3%) of those seen by 19 May and 58/151 (38.4%) of those seen by 25 May did not stay and nest. Our results demonstrate that a substantial proportion of the earliest arriving individuals at this site are prospecting and gathering information about local conditions before making a decision about going elsewhere to nest.

North American Bird Bander↗
USGS2017

Using optimal transport theory to estimate transition probabilities in metapopulation dynamics

This work considers the estimation of transition probabilities associated with populations moving among multiple spatial locations based on numbers of individuals at each location at two points in time. The problem is generally underdetermined as there exists an extremely large number of ways in which individuals can move from one set of locations to another. A unique solution therefore requires a constraint. The theory of optimal transport provides such a constraint in the form of a cost function, to be minimized in expectation over the space of possible transition matrices. We demonstrate the optimal transport approach on marked bird data and compare to the probabilities obtained via maximum likelihood estimation based on marked individuals. It is shown that by choosing the squared Euclidean distance as the cost, the estimated transition probabilities compare favorably to those obtained via maximum likelihood with marked individuals. Other implications of this cost are discussed, including the ability to accurately interpolate the population's spatial distribution at unobserved points in time and the more general relationship between the cost and minimum transport energy.

Ecological Modelling↗
USGS2016

Roseate Tern breeding dispersal and fidelity: Responses to two newly restored colony sites

We used 22 yr of capture–mark–reencounter (CMR) data collected from 1988 to 2009 on about 12,500 birds at what went from three to five coastal colony sites in Massachusetts, New York, and Connecticut, United States, to examine spatial and temporal variation in breeding dispersal/fidelity rates of adult Roseate Terns ( Sterna dougallii ). At the start of our study, Roseate Terns nested at only one site (Bird Island) in Buzzards Bay, Massachusetts, but two more sites in this bay (Ram and Penikese Islands) were subsequently recolonized and became incorporated into our CMR metapopulation study. We examined four major hypotheses about factors we thought might influence colony-site fidelity and movement rates in the restructured system. We found some evidence that colony-site fidelity remained higher at long-established sites compared with newer ones and that breeding dispersal was more likely to occur among nearby sites than distant ones. Sustained predation at Falkner Island, Connecticut, did not result in a sustained drop in fidelity rates of breeders. Patterns of breeding dispersal differed substantially at the two restored sites. The fidelity of Roseate Terns at Bird dropped quickly after nearby Ram was recolonized in 1994, and fidelity rates for Ram soon approached those for Bird. After an oil spill in Buzzards Bay in April 2003, hazing (deliberate disturbance) of the terns at Ram prior to the start of egg-laying resulted in lowering of fidelity at this site, a decrease in immigration from Bird, and recolonization of Penikese by Roseate Terns. Annual fidelity rates at Penikese increased somewhat several years after the initial recolonization, but they remained much lower there than at all the other sites throughout the study period. The sustained high annual rates of emigration from Penikese resulted in the eventual failure of the restoration effort there, and in 2013, no Roseate Terns nested at this site.

Connecticut, Massachusetts, New York, Rhode Island↗
USGS2016

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

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.

Ibis↗
USGS2016

Quantifying the effects of research band resighting activities on staging terns in comparison to other disturbances

Avian research that involves potential disturbance to the study species may have unintended fitness consequences and could lead to biases in measurements of interest. The effects of band resighting on the behavior of mixed-species flocks of staging waterbirds were evaluated against recreational pedestrian activity that was expected to cause flushing. We found a model with additive effects of distance (near, 0-50 m, or far, 50-200 m) and disturbance type (researcher or pedestrian) best explained flock behaviors. The proportion of staging flocks that flushed in response to pedestrians was greatest when pedestrians were within 50 m of the flock. Virtually no flushes were observed in response to researchers, regardless of distance. These results could assist in alleviating concerns that accepted protocols used for intensive band resighting studies on staging seabirds of special conservation status, such as Roseate ( Sterna dougallii ) and Common ( S. hirundo ) terns, may have adverse effects. Our framework could be used by others to test the effects of similar research on sensitive species.

Waterbirds↗
USGS2012

Morphometric sexing of Northwest Atlantic Roseate Terns

A difficulty in the study of monomorphic species is the inability of observers to visually distinguish females from males. Based on a sample of 745 known-sex birds nesting at Bird Island, MA, USA, a discriminant function analysis (DFA) was used to sex Roseate Terns ( Sterna dougallii ) of the Northwest Atlantic population using morphological measurements. DFA using only the total length of the head (including the bill) correctly identified the sex of approximately 86% of the terns, which increased to 88% if both members of a pair were measured. Including additional measurements increased these percentages slightly, to 87% and 90%, respectively. These levels of accuracy are generally higher than those reported for other species of terns. Because female-female pairs are frequent in this population, one cannot assume that the member of a pair with the larger head is a male, and additional discriminant functions were developed to help separate female-female from male-female pairs.

Massachusetts↗
USGS2010

Modelling postfledging survival and age-specific breeding probabilities in species with delayed maturity: A case study of Roseate Terns at Falkner Island, Connecticut

We modeled postfledging survival and age-specific breeding probabilities in endangered Roseate Terns (Sterna dougallii) at Falkner Island, Connecticut, USA using capture-recapture data from 1988-1998 of birds ringed as chicks and as adults. While no individuals bred as 2-yr-olds during this period, about three-quarters of the young that survived and returned as 3-yr-olds nested, and virtually all surviving birds had begun breeding by the time they reached 5 years of age. We found no evidence of temporal variation in age of first breeding of birds from different cohorts. There was significant temporal variation in the annual survival of adults and the survival over the typical 3-yr maturation period of prebreeding birds, with extremely low values for both groups from the 1991 breeding season. The estimated overwinter survival rate (0.62) for adults from 1991-1992 was about three-quarters the usual rate of about 0.83, but the low survival of fledglings from 1991 resulted in less than 25% of the otherwise expected number of young from that cohort returning as breeding birds; this suggests that fledglings suffered a greater proportional decrease in survival than did adults. The survival estimates of young from 1989 and 1990 show that these cohorts were not negatively influenced by the events that decimated the young from 1991, and the young from 1992 and 1993 had above-average survival estimates. The apparent decrease since 1996 in development of fidelity of new recruits to this site is suspected due mainly to nocturnal disturbance and predation of chicks causing low productivity.

Connecticut↗
USGS2009

Modeling individual animal histories with multistate capture–recapture models

Many fields of science begin with a phase of exploration and description, followed by investigations of the processes that account for observed patterns. The science of ecology is no exception, and recent decades have seen a focus on understanding key processes underlying the dynamics of ecological systems. In population ecology, emphasis has shifted from the state variable of population size to the demographic processes responsible for changes in this state variable: birth, death, immigration, and emigration. In evolutionary ecology, some of these same demographic processes, rates of birth and death, are also the determinants of fitness. In animal population ecology, the estimation of state variables and their associated vital rates is especially problematic because of the difficulties in sampling such populations and detecting individual animals. Indeed, early capture–recapture models were developed for the purpose of estimating population size, given the reality that all animals are not caught or detected at any sampling occasion. More recently, capture–recapture models for open populations were developed to draw inferences about survival in the face of these same sampling problems. The focus of this paper is on multi‐state mark–recapture models (MSMR), which first appeared in the 1970s but have undergone substantial development in the last 15 years. These models were developed to deal explicitly with biological variation, in that animals in different “states” (classes defined by location, physiology, behavior, reproductive status, etc.) may have different probabilities of survival and detection. Animal transitions between states are also stochastic and themselves of interest. These general models have proven to be extremely useful and provide a way of thinking about a remarkably wide range of important ecological processes. These methods are now at a stage of refinement and sophistication where they can readily be used by biologists to tackle a wide range of important issues in ecology. In this paper, we draw together information on the state of the art in multistate mark–recapture methods, explaining the models and illustrating their use. We provide a modeling philosophy and a series of general principles on how to conduct analyses. We cover key issues and features, and we anticipate the ways in which we expect the models to develop in the years ahead.

Advances in Ecological Research↗
USGS2008

Juvenile survival in a tropical population of roseate terns: Interannual variation and effect of tick parasitism

Many demographic studies on long-lived seabirds have focused on the estimation of adult survival, but much less is known about survival during the early years of life, especially in tropical species. We report analyses of a capture–recapture dataset of 685 roseate terns ringed as fledglings and adults between 1998 and 2005 on Aride Island, Seychelles, and recaptured/resighted at the same colony site over a 5 yr (2002 to 2006) period. A multistate model was used to estimate survival for different age classes, including juvenile (first-year) birds returning as non-breeding prospectors. The effect of infestation by parasites (ticks) on survival was also examined. Overall, the estimated return of first-year individuals to the natal colony was very variable, ranging from 2 to 22%. Conditioned on survival, the probability of returning from Age 2 yr onwards increased to 70%. Survival rates were best modeled as time-specific, with estimates varying from 0.02 to 1.00 (mean 0.69) in first-year birds with a marked negative effect of tick infestation. In older birds (minimum age of 2 yr), the annual estimates fell between 0.69 and 0.86 (mean 0.77). Using a components of variance approach for estimation of year-to-year variation, we found high temporal variability for first-year individuals (coefficient of variation [CV] = 65%) compared to much less variation in the survival rate of older birds (CV = 9%). These findings agree with the life-history prediction that demographic rates of juveniles are usually lower and more variable than those of older individuals. Our results are also consistent with the predicted negative effect of tick parasitism on juvenile survival. Compared with data from other roseate tern populations, survival over the first 2 yr (Age 0 to 2 yr) was 18 to 40% higher in this study, suggesting that a high ‘young’ survival rate may be an important demographic trait in this tropical population to compensate for the low annual reproductive success. Our data show that estimating survival of young individuals may be crucial to elucidating the demographic tactics of seabirds.

Marine Ecology Progress Series↗
USGS2007

Response of roseate tern to a shoreline protection project on Falkner Island, Connecticut

Construction was initiated following the 2000 tern breeding season for Phase 1 of a planned two-phase "Shoreline Protection and Erosion Control Project" at the Falkner Island Unit of the USFWS Stewart B. McKinney National Wildlife Refuge located in Long Island Sound off the coast of Guilford, CT. When the Common Tern ( Sterna hirundo ) and federally endangered Roseate Tern ( S. dougallii ) arrived in spring 2001, they encountered several major habitat changes from what had existed in previous years. These changes included: a rock revetment covering most of the former nesting habitat on the beach from the northwestern section around the northern tip and covering about 60% of the eastern side; an elevated 60- x 4-m shelf covering the beach and lower bank of the southwestern section; and about 2,000 sq m of devegetated areas on top of the island on the northeast side above the revetment, and about one-third of the southern half of the island. The southwest shelf was created by bulldozing and compacting extra construction fill and in situ materials. This shelf differed in internal structure from the main revetment on the north and eastern sections of the island because it lacked the deep internal crevices of the revetment. The deep internal crevices were created from the large stones and boulders (up to 2 tons) used in the construction of the main revetment. Small rock and gravel was used to fill the crevices to within 3 feet (0.9 m) of the surface of the revetment. Because half-buried tires and nest boxes for the six Roseate Tern ( Sterna dougallii ) sub-colony areas were deployed in similar patterns on the remaining beach, and nest boxes were placed on the newly elevated shelf areas several meters above previous locations on the now-covered beach areas, the distribution of Roseate Tern nests did not change much from 2000 to 2001. However, the movements of Roseate Tern chicks - in many cases led by their parents towards traditional hiding places - into the labyrinth of subterranean channels, especially in the main revetment area, made it difficult to measure chick growth and productivity as had been done for more than 12 years prior to construction. Also, observations of color-banded adults that were unable to locate and feed their young inside the main revetment, and of adults returning to courtship behavior and renesting after having hatched chicks from their initial clutches, indicated that a minimum of 20% of the chicks (mostly first hatched A-chicks, which usually have high rates of survival to fledging) that entered the main revetment died after doing so in 2001. The mortality rate of Roseate Tern chicks that entered the secondary revetment on the southwest shelf, however, was not unusually high in 2001. In an attempt to reduce the likelihood of nesting and chick losses in these sub-colonies, a research team led by the USGS in 2002-2003 did not put nest boxes on the northeast and east shelf areas where previous losses had been high. However, losses of tern eggs and young chicks to predatory Black-crowned Night Herons ( Nycticorax nycticorax ) were so great in 2002-2003 that few Roseate Tern chicks survived long enough to move into the main revetment area and little comparative survival data were collected. The USFWS continues to remove predatory night herons, to monitor the location and success of nesting Roseate Terns and to fill in some of problem areas near the tern nests in the main revetment. The extensive chick-searching fieldwork and observational procedures used by the USGS-led research team to determine the growth and survival of the Roseate Tern chicks at Falkner Island were not used in 2004-2005. The number of chicks lost in the revetment during these years is not known. Without additional fill, loss of chicks of this endangered species in the main revetment may rise again even though the night heron predation problem has been reduced.

Connecticut↗
USGS2005

Sex ratio and early growth patterns of Roseate Tern chicks during five breeding seasons at Falkner Island, Connecticut, USA

Roseate Tern ( Sterna dougallii ) nests were monitored at Falkner Island, Connecticut, USA between 1998 and 2002. A total of 586 chicks were sexed and their growth measured during the first three days. These data were used to derive growth parameters and predict survival to fledging with high confidence. In contrast to a previous study in Massachusetts, we found no sex-ratio bias at hatching in any single year or in all years combined, nor was there a bias at fledging in all years combined, or in any single year. This difference is interesting because both colonies exhibit a female-biased sex ratio at breeding. After controlling for other factors, there was no difference in early growth or survival between male and female chicks, consistent with our previous studies and with the hypothesis that differences in growth and survival between males and females observed in other species are due to sexual size dimorphism.

Connecticut↗