Michael P. Ward

Habitat selection by dispersing yellow-headed blackbirds: evidence of prospecting and the use of public information

In migratory birds individuals may prospect for potential breeding sites months before they attempt to breed and should use the cues most predictive of future reproductive success when selecting a breeding site. However, what cues individuals use when prospecting and which cues are used in selecting a breeding site are unknown for most species. I investigated whether yellow-headed blackbirds (Xanthocephalus xanthocephalus) prospect for future breeding sites and whether they select breeding habitats based on food availability, male or female density, or the average number of young produced per female in the previous year. Although it is often assumed that migratory birds prospect for potential breeding sites at the end of the breeding season, I investigated this by recording all visits to sites early and late in the breeding season. I found that males and females who visited sites other than the site at which they bred were more likely to disperse than individuals only observed at the site where they bred, and that males and females were more likely to prospect late in the breeding season. Both food availability and density in yearx were not predictive of the number of young per female in yearx+1; however, the number of young produced per female at a site in yearx was predictive of the number of young per female in yearx+1. As expected, dispersers used the most informative cue, the number of young per female and moved to sites with a relatively high number of young per female. This study suggests that individuals prospect for potential breeding sites late in the breeding season when they can use information gathered from the reproductive success of other individuals (i.e., public information) to select a breeding site.

Fat, weather, and date affect migratory songbirds' departure decisions, routes, and time it takes to cross the Gulf of Mexico.

Significance Bird migration has captivated the attention of scientists and lay people for centuries, but many unanswered questions remain about how birds negotiate large geographic features during migration. We tracked songbirds across the Gulf of Mexico to investigate the factors associated with birds’ departure decisions, arrival at the Yucatan Peninsula (YP), and crossing times. Our findings suggest that a bird’s fat reserves and low humidity, indicative of favorable synoptic weather patterns, shape departure decisions. Fat, date, and wind conditions predict birds’ detection in the YP. This study highlights the complex decision-making process involved in crossing the Gulf and its effects on migratory routes and speeds. A better understanding of the factors influencing migration across these features will inform conservation of migratory animals. Approximately two thirds of migratory songbirds in eastern North America negotiate the Gulf of Mexico (GOM), where inclement weather coupled with no refueling or resting opportunities can be lethal. However, decisions made when navigating such features and their consequences remain largely unknown due to technological limitations of tracking small animals over large areas. We used automated radio telemetry to track three songbird species (Red-eyed Vireo, Swainson’s Thrush, Wood Thrush) from coastal Alabama to the northern Yucatan Peninsula (YP) during fall migration. Detecting songbirds after crossing ∼1,000 km of open water allowed us to examine intrinsic (age, wing length, fat) and extrinsic (weather, date) variables shaping departure decisions, arrival at the YP, and crossing times. Large fat reserves and low humidity, indicative of beneficial synoptic weather patterns, favored southward departure across the Gulf. Individuals detected in the YP departed with large fat reserves and later in the fall with profitable winds, and flight durations (mean = 22.4 h) were positively related to wind profit. Age was not related to departure behavior, arrival, or travel time. However, vireos negotiated the GOM differently than thrushes, including different departure decisions, lower probability of detection in the YP, and longer crossing times. Defense of winter territories by thrushes but not vireos and species-specific foraging habits may explain the divergent migratory behaviors. Fat reserves appear extremely important to departure decisions and arrival in the YP. As habitat along the GOM is degraded, birds may be limited in their ability to acquire fat to cross the Gulf.

AdaptSens: An Adaptive Data Collection and Storage Service for Solar-Powered Sensor Networks

In this paper, we present AdaptSens: a reliable data collection and storage system for solar-powered sensor networks. Unlike battery-operated devices, solar-powered systems have a less predictable energy supply and their ability to harvest energy depends on past spending, thereby creating incentives for adaptive matching of energy supply and demand. Our storage system is novel in its layered architecture and its incremental layer activation mechanism. AdaptSens provides a set of functions, in separate layers, such as sensory data collection, replication (to prevent failure-induced data loss), and storage balancing (to prevent depletion-induced data loss). The mechanism utilizes surplus energy when available by activating more layers, and resorts to progressively more energy-efficient (partial hibernation) modes when energy is scarce. Best reliability is achieved when all layers are active but meaningful intermediate modes allow different degrees of energy conservation. The efficacy of AdaptSens in trading off reliability for energy is tested on both an outdoor system and an indoor testbed. Evaluation results show that AdaptSens minimizes the sum of all data losses when combining the energy, storage and node failure factors.

Evaluation of Automated Radio Telemetry for Quantifying Movements and Home Ranges of Snakes

Abstract We evaluated an automated telemetry system that can dramatically increase the amount of activity and spatial data collected for snakes. We developed methods for analyzing data from single automated receiving units (ARUs) and ARU arrays, compared results from ARUs with conventional hand tracking, and assessed previously untested assumptions used in conventional telemetry, using data from ratsnakes (Pantherophis spp.) in Texas and Illinois. ARU data indicated that ratsnakes spent most of their time in small home ranges (mean = 25 ha) but engaged in forays of up to 1.5 km from their core-use areas, suggesting this species may engage in central place foraging. Forays inflated home-range sizes greatly if areas were estimated using minimum convex polygons rather than 95% kernels. Large numbers of locations generated by ARUs produce more reliable home-range estimates than those from hand tracking. ARU data indicated that snakes moved in response to observers during hand tracking. Daily hand tracking produced reliable estimates of distances moved but underestimated distances by a factor of 4 when snakes were tracked every 5 days. Drawbacks of ARUs are that the error associated with individual locations exceeds that for hand-tracked locations and that the costs exceed those for hand tracking. Automated receivers can increase data greatly from radio-tracked snakes, providing novel insights unavailable from conventional hand tracking. There are drawbacks to this technology, some of which will vary among study species; therefore, researchers should evaluate the appropriateness of the technology for both the study species and the questions being asked.

Seasonal responses of avian communities to invasive bush honeysuckles (Lonicera spp.)

Invasive bush honeysuckles, Lonicera spp., are widely viewed as undesirable; however, the effects of Lonicera spp. on native fauna are largely unknown. We investigated how breeding and overwintering bird communities respond to the presence of Lonicera spp. by comparing communities in forested areas with Lonicera spp. to those with a native shrub understory. The dense understory created by Lonicera spp. was associated with a change in the breeding bird community. We found large increases in the densities of understory bird species (e.g. northern cardinals) and decreases in select canopy species (e.g. eastern wood-pewees) in Lonicera spp. sites. In winter, we observed greater densities of frugivorous birds (e.g. American robins) likely due to the fruits that remain on Lonicera spp.; however, there was no difference in the community composition between sites with and without Lonicera spp. Given the widespread distribution of Lonicera spp., this invasive species may facilitate the population increase and range expansion of selected bird species. Many bird species appear to utilize Lonicera spp. for nesting and foraging; therefore, its removal should be accompanied by restoring native shrubs that provide needed resources.

Sex-specific differences in site fidelity and the cost of dispersal in yellow-headed blackbirds

Male migratory birds tend to be more faithful than females to previous breeding sites, suggesting sex differences in costs or benefits of dispersal. In Illinois, greater site fidelity by male yellow-headed blackbirds (Xanthocephalus xanthocephalus) was associated with reduced reproductive success the following year for dispersers relative to non-dispersers. Dispersing females suffered no reduction in reproductive success the following year. Males that attracted few social mates, and thus had low reproductive success, were more likely to disperse, whereas females dispersed in response to low-patch reproductive success, regardless of their individual performance. Males that dispersed appeared to be successful acquiring territories because none was observed as a floater. The rate of dispersal by males in this low-density population was greater than in more dense populations where dispersing males may be less successful at acquiring territories. Despite success at obtaining territories, males that dispersed acquired territories on the periphery of wetlands where fewer females nested, resulting in lower reproductive success. In the second year after dispersing, however, males moved onto more central territories where they acquired larger harems. Thus, dispersal by males may be a long-term strategy requiring at least 2 years for benefits to be realized. Long-term success was enhanced because dispersing males moved to wetlands on which reproductive success was higher than on the wetlands they left. In addition to demonstrating that both individual and patch reproductive success affect dispersal decisions, these data indicate that when evaluating costs and benefits of dispersal, researchers should use a time frame beyond 1 year.

The active nightlife of diurnal birds: extraterritorial forays and nocturnal activity patterns

Most birds are socially monogamous, diurnally active and have small home ranges. These birds occasionally undertake extraterritorial forays, presumably to seek extrapair copulations. We used automated radiotelemetry to examine nocturnal forays and activity of a diurnal, socially monogamous passerine, the yellow-breasted chat, Icterina virens. Males and females forayed during both day and night, but night forays were more common. In addition to varying between day and night, there were sex- and breeding-stage-specific differences in foraying behaviour. Males forayed more than females and more frequently when their female was not fertile. Conversely, females primarily forayed when fertile. We suggest that females foray at night to avoid detection, because their mates knowledge of potential extrapair copulations may result in harassment or decreased parental care. Both sexes were nocturnally active; however, the activity of males peaked when their mates were fertile, probably to prevent their mates from foraying and guarding them from foraying males. The nocturnal behaviour of chats suggest that extraterritorial forays may be more common than previously thought and that nocturnal behaviours may be crucial for understanding the strategies males and females use to acquire extrapair copulations.

Effects of temperature, moon phase, and prey on nocturnal activity in Ratsnakes: An automated telemetry study

Abstract Nocturnal activity is important for many animals, but difficulty in documenting that activity has hampered efforts to understand factors that influence when animals are active at night. We used automated radiotelemetry to provide the first detailed tests of the hypothesis that the nocturnal activity of free-ranging snakes should be influenced by temperature, moon phase, and prey abundance by using data for Ratsnakes (Pantherophis spp.) from Texas and Illinois. Ratsnakes exhibited some nocturnal behavior throughout their active season in both Texas and Illinois, although snakes were much more active at night in Texas than in Illinois. Texas snakes transitioned from primarily diurnal activity to primarily nocturnal activity over this snakes active season, whereas Illinois snakes were always most active in the middle of the day. For both populations, nocturnal activity was positively related to temperature but unrelated to moon phase. Ratsnakes in Texas exhibited a stepwise increase in nocturnal activity in mid-summer, independent of temperature and coincident with the shift in their diet to almost exclusively mammals active at night. Given the ability of snakes in both populations to be active at night when temperatures allow, warming climates could lead to an increase in nocturnal activity, with consequences for both the snakes and the species on which they prey.

Clinical Pharmacokinetics of Benzodiazipines

B enzodiazepines were first introduced in 1961 with the release of chlordiazepoxide. As opposed to the barbiturates the benzodiazepines had a very low potential for respiratory depression and a high therapeutic index on overdose thus, the benzodiazepines became hailed as a safer medication for the treatment of anxiety. Since that time more than 3000 benzodiazepines have been synthesized with more than 20 currently in use on an international spectrum.1 During the mid-seventies, diazepam was the number one drug prescribed in the United States. Eightyseven million prescriptions were filled for benzodiazepines in 1973.2 Recently, benzodiazepine usage has come under scrutiny secondary to the emergence of psychologic as well as physiologic addiction, abuse, and withdrawal phenomena. Guidelines have been established for the use of these agents “ as well as many articles written concerning addiction potential of these agents and experiences of benzodiazepine withdrawa1.93 The characterization of the pharmacokinetic and pharmacodynamic properties of the benzodiazepines has not been fully elucidated. A thorough understanding of the known pharmacokinetic and pharmacodynamic data concerning these agents is important to effectively use the benzodiazepines for the treatment of indicated disease states.

When to use social cues: Conspecific attraction at newly created grasslands

ABSTRACT Social cues are often used by birds when selecting breeding habitats, however, little is known about the timing and influence of social cues within or across seasons. The ontogeny of social information within newly available habitat is essentially unknown and potentially relevant to habitat management, as the primary approach of many conservation initiatives is to simply create habitat. We investigated the influence of conspecific attraction via social cues (conspecific playbacks) on newly created grasslands for Grasshopper Sparrows (Ammodramus savannarum) in Central Illinois over a 2-year period. We found that Grasshopper Sparrows quickly locate and settle at newly created grasslands without the need for social cues, however, social cues are used later in the season. At sites where social cues (i.e. conspecific vocalizations) were broadcast the densities of Grasshopper Sparrows were nearly double that of sites without the additional social cues, however, this difference occurred later in the breeding season. We suggest that social cues are more valuable for Grasshopper Sparrows later in the breeding season as a potential cue of the reproductive success of individuals currently at the site, and therefore future reproduction at the site. Grassland birds are experiencing large population declines and the primary conservation approach is to provide additional habitat. By understanding how grassland birds select breeding sites we can better develop and implement conservation plans.