Daniel Saenz

Abiotic correlates of anuran calling phenology: the importance of rain, temperature, and season

ABSTRACT We surveyed anuran calls nightly at eight ponds in eastern Texas from 1 January 2001 through 31 December 2002. Air temperatures and daily rainfall also were recorded for each of the sites. Eastern Texas contains a diverse temperate anuran fauna and a climate that provides a range of conditions for anuran reproduction. During our study, we measured air temperatures that fluctuated seasonally with extremes from 0 to 29 C at 2100 h. We found rainfall to be generally abundant with occasional flooding events, however, prolonged periods of no precipitation were also observed. Given the level of anuran diversity and the amount of seasonal variation in temperature and rainfall in our temperate climate we expected to find a variety of breeding strategies. Results from our analyses did indeed suggest five basic breeding strategies based on anuran calling: (1) breeding within a predictable season (summer) independent of local weather patterns; (2) breeding opportunistically within a predictable season (summer) dependent on local rainfall; (3) breeding opportunistically within a predictable season (winter) dependent on local temperature; (4) breeding opportunistically dependent on local flood level rainfall events; (5) breeding opportunistically year round dependent on local temperature in the winter and local rainfall in the summer.

Dietary Overview of Hemidactylus turcicus with Possible Implications of Food Partitioning

A stomach content analysis was conducted on Hemidactylus turcicus, the Mediterranean gecko, from 19 April 1990 to 15 October 1990, on the campus of Stephen F. Austin State University, Nacogdoches, Texas. Geckos (N = 167) were placed into four size groups based on snout-vent-length ( 1.52 m to c 3.05 m, and > 3.05 m). Stomach contents were analyzed and sex, size, and microhabitat groups were compared using Schoeners percent overlap index. Volumet- rically, the most important prey items taken were Orthoptera, Lepidoptera, and Isopoda. Geckos of different size groups showed some differences in diet. The greatest difference occurred between the smallest and largest size groups. A significant positive correlation was found between gecko size and prey size (r = 0.24, P = 0.0008). Differences in the diets of geckos inhabiting different microhabitats were very evident. Geckos occupying high perch sites ate more flying prey while geckos at lower perch sites ate more ground- dwelling prey.

AVIAN COMMUNITY RESPONSE TO SOUTHERN PINE ECOSYSTEM RESTORATION FOR RED-COCKADED WOODPECKERS

Abstract The effects of Red-cockaded Woodpecker (Picoides borealis) management on nontarget birds is not widely known. Intensive management for pine specialists such as the Red-cockaded Woodpecker may negatively impact both Nearctic-Neotropical and Temperate Zone migrants associated with hardwood vegetation. To evaluate possible positive and negative associations, we surveyed avian communities from 1995–1997 using point counts within managed Red-cockaded Woodpecker cavity tree clusters and mature forest control sites in longleaf pine (Pinus palustris) and loblolly (P. taeda)-shortleaf (P. echinata) pine habitats. In general, sites managed for Red-cockaded Woodpeckers supported more diverse and numerous bird populations than mature forest control sites. During the breeding season in loblolly-shortleaf and longleaf pine habitats, respectively, species richness was 47% and 23% greater, avian abundance was 57% and 65% greater, and bird species diversity was 25% and 21% greater within managed Red-cockaded Woodpecker cluster sites than within control sites. During winter, species richness and avian abundance each were 52% higher within managed Red-cockaded Woodpecker cluster sites than control sites in loblolly-shortleaf pine habitat.

RED-COCKADED WOODPECKER NEST-CAVITY SELECTION: RELATIONSHIPS WITH CAVITY AGE AND RESIN PRODUCTION

We evaluated selection of nest sites by male Red-cockaded Woodpeckers (Pi- coides borealis) in Texas relative to the age of the cavity when only cavities excavated by the woodpeckers were available and when both naturally excavated cavities and artificial cavi- ties were available. We also evaluated nest-cavity selection relative to the ability of naturally excavated cavity trees to produce resin, which is used by the woodpeckers to maintain a barrier against predation by rat snakes (Elaphe spp.). Longleaf pines (Pinus palustris) selected by breeding males as nest trees produced significantly greater resin yields at 2, 8, and 24 h post-wounding than cavity trees used for roosting by other group members. This preference was observed in loblolly pine (I! taeda) and shortleaf pine (I? echinata) cavity trees only at the 2-h resin-sampling period. When only naturally excavated cavities were available, Red-cock- aded Woodpeckers in both longleaf pine and loblolly-shortleaf pine habitat selected thenew- est cavities available for their nest sites, possibly as a means to reduce parasite loads. When both naturally excavated and artificial cavity inserts were available, Red-cockaded Wood- peckers continued to select the newest cavity for nesting in loblolly-shor tleaf pine habitat but not in longleaf pine habitat. Resin production in existing longleaf pine nest trees re- mained sufficient for continued use, whereas resin production in loblolly pine and shortleaf pine nest trees decreased through time, probably because of woodpecker activity at resin wells. For these latter tree species, breeding males switched to newer cavities and/or cavity trees with higher resin yields. Received 7 )uly 1997, accepted 11 November 1997.

The longevity of large pine snags in eastern Texas

Abstract Habitat for cavity-nesting wildlife is closely tied to the availability of standing dead trees (snags). Large snags (>40 cm dbh) are particularly important because they provide cavity-excavation substrate for both large and small cavity excavators. Historically in the southern United States, common belief has been that the utility of pine (Pinus spp.) snags for cavity nesters occurs for only a short period of time after tree death because pine snags quickly decay and fall to the ground. We studied the deterioration rate and ultimate falling of large pine snags in eastern Texas over a 20-year period (1983–2003). Coinciding with our annual checks of red-cockaded woodpecker (Picoides borealis) cavity-tree clusters, we checked the status and height of all red-cockaded woodpecker cavity trees that died. We determined the cause of death and tree species of 136 cavity tree snags (x̄=25.4 m at death) and monitored their height annually until they were <1 m in height. Five years after tree death, 92 snags (67.6%) were still standing and averaged 13.9 m in height. Ten years after tree death, 21 snags (15.4%) were still standing and averaged 10.0 m in height. After 15 years 4 snags (2.9%) averaging 5.3 m in height still remained standing. Two snags (1.5%), averaging 2.7 m in height, survived through 19 years but had fallen by the end of the twentieth year. Pines dying from wind snap at mid-bole survived longer as snags (x̄=9.7 years) than pines killed by bark-beetles (Dendroctonus spp.) (x̄= 5.9 years). Longleaf pine (Pinus palustris) snags remained standing longer (x̄=8.0 years) than loblolly pine (P. taeda) snags (x̄=6.0 years) (P<0.05), but not longer (P>0.05) than shortleaf pine (P. echinata) snags (x̄=6.6 years).

ALLOMETRY, SEXUAL SIZE DIMORPHISM, AND NICHE PARTITIONING IN THE MEDITERRANEAN GECKO (HEMIDACTYLUS TURCICUS)

Abstract Hemidactylus turcicus is a small gekkonid lizard native to the Middle East and Asia that is known to exhibit sexual dimorphism in head size. Several potential explanations exist for the evolution and maintenance of sexual dimorphism in lizards. We tested 2 of these competing hypotheses concerning diet partitioning and differential growth. We found no differences in average meal size (volume) or in any single dimension of prey size for similarly sized males and females. Allometric patterns of increases in head size also were measured in males and females. We found that males exhibited a mixture of isometric and positively allometric patterns of head size increase, whereas females exhibited isometric and negatively allometric patterns. Thus, we concluded that sexual dimorphism in head size is not the result of diet partitioning but instead of differential growth patterns following sexual maturity in males and females.

Group size and nest success in Red-cockaded Woodpeckers in the West Gulf Coastal Plain: helpers make a difference

Abstract We studied the relationships between Red-cockaded Woodpecker (Picoides borealis) group size and nest productivity. Red-cockaded Woodpecker group size was positively correlated with fledging success. Although the relationships between woodpecker group size and nest productivity measures were not statistically significant, a pattern of increasing clutch size and number of hatchlings with increasing group size was apparent. The presence of helpers appeared to enhance the survival of nestlings between hatching and fledging. The contribution that helpers make to nestling feeding and incubation, cavity excavation, and territory defense appears to have a positive effect on nest productivity. A threshold number of helpers may be necessary before a significant benefit for fledging success is realized. Nests with four and five group members fledged more young than nests with two or three group members. Whether partial brood loss occurred or not within a nest was primarily a function of clutch size and the number of hatchlings. Although partial brood loss did affect the number of young fledged from individual nests by removing young from nests with high numbers of hatchlings, woodpecker group size appeared to be the primary determinant of fledging success.

Palatability of Twelve Species of Anuran Larvae in Eastern Texas

Abstract We tested the palatability of 12 species of anuran larvae that occur in eastern Texas using four common predators. Palatability was determined by offering larvae to predators and recording the behavior of the predator. We also tested for ontogenetic shifts in palatability in twelve species of anuran larvae. Incilius nebulifer, Anaxyrus woodhousii, Lithobates catesbeianus, L. clamitans and L. sphenocephalus all showed evidence of unpalatability in laboratory experiments. These noxious larval anurans also showed ontogenetic shifts in palatability to one or more predators by becoming more palatable throughout development. Predator tolerance to noxiousness also played a key role in predation trials. Bluegills were the least tolerant, followed by green sunfish and dragonfly larvae. Crayfish had the highest tolerance to noxiousness.

Red-cockaded woodpecker nestling provisioning and reproduction in two different pine habitats

Abstract We obtained nestling provisioning and reproductive data from 24 Red-cockaded Woodpecker (Picoides borealis) groups occupying two different pine habitats—longleaf pine (Pinus palustris) and a mixture of loblolly (P. taeda) and shortleaf pine (P. echinata)—in eastern Texas during 1990 and 1991. Habitat data were collected within 800 m of each groups cavity-tree cluster. Feeding trips per nest and prey biomass per feeding trip were significantly greater in loblolly-shortleaf pine habitat. There were few significant correlations between reproductive/provisioning and habitat variables in either pine habitat. Pines dying from infestation by southern pine beetles (Dendroctonus frontalis) were more common in loblolly-shortleaf than in longleaf pine habitat. In addition, adult male Red-cockaded Woodpeckers weighed more in loblolly-shortleaf pine habitat. Indices of southern pine beetle abundance in loblolly-shortleaf pine habitat were negatively correlated with number of feeding trips per nestling, but positively correlated with prey biomass delivered to nestlings. We hypothesize that the greater abundance of southern pine beetles and associated arthropods in loblolly-shortleaf pine habitat, and the resulting higher frequency of dying pines containing an abundant food source, were associated with an elevated prey biomass available to both nestling and adult Red-cockaded Woodpeckers.

Does Red-Cockaded Woodpecker Excavation of Resin Wells Increase Risk of Bark Beetle Infestation of Cavity Trees?

WEATHERHEAD, P. J., AND S. B. McRAE. 1990. Brood care in American Robins: Implications for mixed reproductive strategies by females. Animal Behaviour 39:1179-1188. WESTNEAT, D. F. 1987. Extrapair fertilizations in a predominantly monogamous bird: Genetic evidence. Animal Behaviour 35:877-886. WESTNEAT, D. F. 1990. Genetic parentage in the Indigo Bunting: A study using DNA fingerprinting. Behavioral Ecology and Sociobiology 27:6776. WESTNEAT, D. F., AND E. M. GRAY. 1998. Breeding synchrony and extrapair fertilizations in two populations of Red-winged Blackbirds. Behavioral Ecology 9:456-464. WESTNEAT, D. F., AND P. W. SHERMAN. 1997. Density and extra-pair fertilizations in birds: A comparative analysis. Behavioral Ecology and Sociobiology 41:205-215. WESTNEAT, D. F., P. W. SHERMAN, AND M. L. MORTON. 1990. The ecology and evolution of extra-pair copulations in birds. Current Ornithology 7: 331-369.