Kirk W. Stodola

Elevational and seasonal variation in the foliar quality and arthropod community of Acer pensylvanicum.

ABSTRACT Elevational gradients provide natural experiments for examining how variation in abiotic forces such as nutrient mineralization rates, risk of photodamge, temperature, and precipitation influence plant—insect interactions. At the Coweeta LTER site in the Southern Appalachian Mountains, we examined spatial and temporal variation in striped maple, Acer pensylvanicum, foliar quality and associated patterns in the arthropod community. Variation in herbivore densities was associated more strongly with seasonal variation in plant quality than with spatial variation in quality among three sampling sites. Leaf chewer, but not phloem feeder or arthropod predator, densities increased with elevation. Foliar quality, by our measures, decreased throughout the growing season, with decreases in nitrogen concentrations and increases in lignin concentrations. Foliar quality varied among the three sites but not systematically along the elevational gradient. We conclude that, in this system, temporal heterogeneity in plant quality is likely to be more important to insect herbivores than is spatial heterogeneity and that other factors, such as the abiotic environment and natural enemies, likely have substantial effects on herbivore density.

Biotic and Abiotic Factors Governing Nestling-Period Length in the Ovenbird (Seiurus aurocapilla)

ABSTRACT. In many songbirds, the nesting period for a breeding attempt is extremely short, often lasting only a few weeks. Breeding adults can shorten this period by decreasing the number of eggs laid or reducing the length of the nestling period. Nestling-period length has received little attention in the literature but could have profound effects on annual fecundity, because each day represents a risk of nest depredation. Consequently, we were interested in assessing the biotic and abiotic factors that govern the nestling period in the Ovenbird (Seiurus aurocapilla). We provide evidence that food availability, more than predation pressure and climatic factors, influences nestling-period length, with increases in food availability decreasing the nestling period. We suggest that the nestling period is dictated by physiological constraints, which may be influenced by food availability and, thus, the ability to provision young. However, the greatest variation in nestling period was individual variation among breeding pairs. Thus, we believe that large-scale variation in ecological and environmental factors may determine the physiological constraints of the nestling period but parental behavior and quality within this framework dictate the actual length of the nestling period.

Influence of Tidal Height on Detection of Breeding Marsh Birds Along the Northern Gulf of Mexico

Abstract We studied variation in detection probabilities of several marsh bird species during the breeding season in relation to tidal height (i.e., water level) within several tidal marshes of the northern Gulf of Mexico. Specifically, we examined the influence of tidal height on our ability to detect Clapper Rail (Rallus longirostris), Seaside Sparrow (Ammodramus maritimus), Marsh Wren (Cistothorus palustris), Purple Gallinule (Porphyrio martinica), and Common Moorhen (Gallinula chloropus). Detection of Clapper Rails and Seaside Sparrows increased relative to tidal height while detection of Marsh Wrens decreased. Our results suggest that tidal height influences detection of specific marsh bird species, although these effects may differ geographically. We advocate including collection of tidal height information as a part of the survey protocol for effective monitoring of marsh bird populations.

Seasonal and daily patterns of nocturnal singing in the Field Sparrow (Spizella pusilla)

AbstractNocturnal singing in diurnal birds is poorly described in the literature and is not well understood. Most research has been limited to the documentation of the behavior, with little information regarding the patterns and function of nocturnal song. We used autonomous acoustic recording units and automated detection and classification algorithms to examine the seasonal and nocturnal patterns of song in the Field Sparrow, Spizella pusilla, a diurnal songbird. We used a generalized linear mixed model to investigate the patterns in the probability of recording each of the two song types described for the species (simple and complex) at night from 7938 10-min recordings from 14 different individuals singing in six different grassland patches. We fit different models investigating the influence of date within the season and time period during the night, and compared models using the Bayesian information criterion. Male Field Sparrows sang both simple and complex songs during the early stages of territory settlement and mate acquisition. However, as the breeding season progressed, we detected fewer instances of simple song, while the occurrence of complex song increased, reaching its peak during the height of reproductive activity. The seasonal pattern of simple and complex songs suggests that they may have a similar function at night and during the day, with simple songs used for inter-sexual interactions and complex songs used for intrasexual functions. Consequently, the role and function of nocturnal song may be more important for reproductive activities than previously assumed.ZusammenfassungSaisonale und tägliche Muster des nächtlichen Gesangs bei Klapperammern (Spizella pusilla) Der nächtliche Gesang tagaktiver Vögel ist unzureichend beschrieben und wenig untersucht. Der Großteil der Forschung beschränkte sich auf die Dokumentation dieses Verhaltens mit wenig Informationen zu Mustern und Funktion des nächtlichen Gesangs. Wir nutzen autonome akustische Aufnahmeeinheiten und automatisierte Erfassungs- und Klassifikationsalgorithmen zur Untersuchung der saisonalen und nächtlichen Muster des Gesangs von Klapperammern, Spizella pusilla, einer tagaktiven Singvogelart. In 7938 nächtlichen 10-Minuten-Aufnahmen von 14 verschiedenen singenden Individuen in sechs unterschiedlichen Grünlandflächen analysierten wir die Muster der Aufnahmewahrscheinlichkeit für jeden der beiden Gesangstypen, die für die Art (einfach und komplex) beschrieben sind, mit Hilfe eines generalisierten linearen gemischten Modells. Wir passten verschiedene Modelle an, um den Einfluss des Datums innerhalb der Saison und der zeitlichen Periode während der Nacht zu ermitteln und verglichen die Modelle mit Hilfe des Bayesischen Informationskriteriums. Männliche Klapperammern singen sowohl einfache als auch komplexe Strophen während der frühen Phasen der Revierbesetzung und Partnerwahl. Allerdings stellten wir mit fortschreitender Brutsaison weniger Fälle von einfachem Gesang fest, während das Auftreten von komplexen Gesängen anstieg und seinen Höhepunkt erreichte, als die reproduktive Aktivität am größten war. Das saisonale Muster von einfachen und komplexen Gesängen lässt ähnliche Funktionen während der Nacht und des Tages vermuten, wo einfache Gesänge für intersexuelle Interaktionen und komplexe Gesänge für intrasexuelle Funktionen eingesetzt werden. Folglich könnte die Rolle und Funktion des nächtlichen Gesangs weitaus wichtiger sein für die Reproduktion, als bisher angenommen.

Stopover ecology of American Golden-Plovers (Pluvialis dominica) in Midwestern agricultural fields

ABSTRACT Stopover locations represent critical habitat in the life cycle of migratory birds and the alteration of this habitat can profoundly influence a population. American Golden-Plovers (Pluvialis dominica) migrate though the Midwestern United States each spring, where most natural habitat has been converted to row crop agriculture. We investigated the stopover ecology of the golden-plover in the agricultural matrix of east-central Illinois and west-central Indiana between 2008 and 2012. We found that golden-plovers remained in the region for ∼45 days and individuals spent on average 24 days in the area before departing to the northwest. During a period of peak migration, golden-plovers preferred fields with standing water and, to a lesser extent, soybean fields. Over the 45-day stopover duration, golden-plovers moved extensively (shown by a dynamic occupancy model and area used estimation), with some evidence for tilled fields becoming unoccupied at greater rates than untilled fields. The tendency to use fields with standing water and the movement of individuals from tilled fields suggests that food accessibility, rather than food abundance, is likely a critical factor associated with the prolonged stay, movement, and field type selection of golden-plovers. Food accessibility is important to the golden-plover because they undergo molt into breeding plumage in the region and must refuel for the next leg of their migration. The Midwest is a key stopover location for American Golden-Plovers and promoting foraging conditions by manipulating the drainage of agricultural fields, via the temporary blockage of drain tiles, should be a management focus.

Effective use of data from monitoring programs and field studies for conservation decision making: Predictions, designs and models working together

Effective integration of information in conservation decision making requires explicit consideration of conservation goals and objectives, specification of a range of potential actions, and the willingness to use information to assist in making and improving decisions. If these conditions are met, monitoring programs would benefit from the creative interplay between predictions, designs and models. Prediction, a basic component of scientific endeavor, is also a key component of scientific decision-making. Effective application of information to decision making typically requires integration of several types of information in a common framework, including “found” data and retrospective studies, innovative sampling designs, and the use of hierarchical data structures (e.g., demographic studies nested with occupancy sampling and analysis of community structure). Sampling designs can also include quasi-experimentation, in which confounding factors are accounted for by spatial or temporal “controls” or covariates. Hierarchical and state-space modeling, often most effectively performed in a Bayesian framework, provide a unified modeling structure for such designs and data. We illustrate these ideas with the problem of investigating and mitigating the effects of climate change on terrestrial birds in North America. Ecological theory and available data provide predictions about the impacts of global, regional, and local climate changes on avian communities. We outline a hierarchical sampling design providing for assessment and monitoring of key state variables. The design integrates broad-scale metrics such as species richness and turnover from existing monitoring programs, with directed monitoring using combinations of occupancy and capture–mark–recapture sampling to address specific questions of local extinction and colonization as well as demographic rates in relation to latitudinal and altitudinal gradients. The design would incorporate temporal, spatial, and management controls (presence/absence of selective interventions) as feasible, and manipulative experiments such as supplemental feeding to test specific predictions at specific sites. Data would be incorporated into a hierarchical modeling structure directed specifically at informing and updating the predictive management model.

Effective use of Data from Marshbird Monitoring Programs for Conservation Decision-Making

Abstract. Monitoring programs aimed at understanding the population trends of secretive marshbirds can be altered to benefit from the creative interplay between predictions, designs and models, and provide the template for doing so. Effective application of information to decision making typically requires integration of several types of information in a common framework, including “found” data and retrospective studies, innovative sampling designs and the use of hierarchical data structures. Hierarchical and state-space modeling provide a unified modeling structure for such designs and data. These ideas are illustrated with the problem of investigating and mitigating the effects of climate change on secretive marshbirds in coastal North America. How both ecological theory and available data can be used to provide predictions about the impacts of regional and local climate changes on these avian communities are illustrated.

The Emergent Properties of Conspecific Attraction Can Limit a Species’ Ability to Track Environmental Change

Multiple biotic, abiotic, and evolutionary constraints interact to determine a species’ range. However, most species are not present in all suitable and accessible locations. Dispersal ability may explain why many species do not occupy all suitable habitat, but highly mobile species also exhibit a mismatch. Habitat selection behavior where individuals are site faithful and settle near conspecifics could create a social pressure that make a species’ geographic range resistant to change. We investigated this possibility by using an individual-based model of habitat selection where habitat quality moved each year. Our model demonstrated the benefits of conspecific attraction in relatively stable environments and its detrimental influence when habitat quality shifted rapidly. These results were most apparent when adult survival was high, because site fidelity led to more individuals occupying poor-quality habitat areas as habitat quality changed. These individuals attracted other dispersing individuals, thereby decreasing the ability to track shifts in habitat quality, which we refer to as “social inertia.” Consequently, social inertia may arise for species that exhibit site fidelity and conspecific attraction, which may have conservation implications in light of climate change and widespread alteration of natural habitats.

Identifying native and exotic predators of ground-nesting songbirds in subantartic forests in southern Chile

Las aves Passeriformes constituyen el grupo mas diverso y abundante de vertebrados en el archipielago austral de Sudamerica. Sin embargo, se desconocen varios aspectos claves de su ecologia, tales como el exito de nidificacion y sus depredadores. El vison americano ( Neovison vison ) fue introducido a Tierra del Fuego en la decada de 1940 e invadio la Reserva de la Biosfera Cabo de Hornos, al sur del Canal Beagle en 2001. Como nuevo depredador tope, el vison invasor puede tener impactos significativos sobre las especies de aves nativas, incluyendo algunos Passeriformes del bosque que nidifican al nivel del suelo. Para determinar la identidad y el efecto de los depredadores de nidos en el suelo, condujimos un experimento con nidos artificiales y determinamos el impacto de los depredadores en las tasas de supervivencia diarias de nidos en tres tipos de habitats diferentes (matorrales antropogenicos, pastizales de castoreras y bosques). El 65% de los nidos fueron depredados (40% debido al chercan nativo [ Troglodytes musculus ] y 25% debido al vison exotico). Sin embargo, se encontro que el vison fue la causa del 53% del fracaso de los nidos en el matorral antropogenico. Estos resultados demuestran que tanto los depredadores nativos como los exoticos afectan el exito de nidificacion de la avifauna del bosque subantartico, pero el efecto de un depredador tope invasor, como el vison, constituye una nueva amenaza que podria afectar el exito de nidificacion y la sobrevivencia de los adultos.