No abstract

Although the poaching of nestlings for the pet trade is thought to contribute to the decline of many species of parrots, its effects have been poorly demonstrated. We calculated rates of mortality due to nest poaching in 23 studies of Neotropical parrots, representing 4024 nesting attempts in 21 species and 14 countries. We also examined how poaching rates vary with geographic region, presence of active protection programs, conservation status and economic value of a species, and passage of the U.S. Wild Bird Conservation Act. The average poaching rate across all studies was 30% of all nests observed. Thirteen studies reported poaching rates of ≥20%, and four reported rates openface> 70%. Only six studies documented no nest poaching. Of these, four were conducted on islands in the Caribbean region, which had significantly lower poaching rates than the mainland Neotropics. The other two studies that showed no poaching were conducted on the two species with the lowest economic value in our sample ( U.S. retail price). In four studies that allowed direct comparison between poaching at sites with active nest protection versus that at unprotected sites, poaching rates were significantly lower at protected sites, suggesting that active protection efforts can be effective in reducing nest poaching. In those studies conducted both before and after the passage of the U.S. Wild Bird Conservation Act, poaching rates were found to be significantly lower following its enactment than in the period before. This result supports the hypothesis that the legal and illegal parrot trades are positively related, rather than inversely related as has been suggested by avicultural interests. Overall, our study indicates that poaching of parrot nestlings for economic gain is a widespread and biologically significant source of nest mortality in Neotropical parrots.

Parrots (Order Psittaciformes) are secondary cavity-nesters that depend on existing cavities for nest sites, and consume plant resources of fruits, seeds, and flowers that are highly variable, but little is known of resource selectivity by parrots, or how they deal with variable environments. We reviewed published studies of nest-cavity use by parrots, and those evaluating parrot diet and their relationship with food resources. Most studies have been conducted within the last 20 years and these present data on resource use for only one-third of parrot species worldwide. However, basic information on resource requirements is lacking for the vast majority of Psittaciformes, particularly for species from the Asian region. Nesting studies have found that parrots use nest cavities in large trees, high above the ground, with large nest chambers, of 0.5-1 m deep, and entrance diameters related to body size of the parrot species. A few studies demonstrate that parrots select nest sites based on cavity characteristics, which may influence nest success, but a complete evaluation of adaptive nest site selection by Psittaciformes is lacking. Parrots have varied diets and may employ a combination of strategies of diet switching, habitat shifts, and movements to track food resources. This plasticity in diet and foraging strategy may influence the extent to which parrots can respond to anthropogenic pressures of global change. Parrots may also play an important functional role in forest ecosystems, yet little is currently known of plant-animal interactions of parrots, or the impact of parrot populations on forest dynamics. Based on our review of the literature, we suggest that to meet their resource requirements, parrots employ resource selection strategies of hierarchical nest site selection to increase the likelihood of nest success, and plasticity in diet and foraging strategy to track variable food resources. Future studies need to evaluate resource selection and the consequences of this for fitness in order to assess the potential impacts of global change on parrot populations, and to identify characteristics which make species vulnerable to human pressures.

The pattern of food resource availability and use by Lilac-crowned Parrots (Amazona finschi) was evaluated in tropical dry forest of the Reserva de la Biosfera Chamela-Cuixmala, western Mexico. Monthly fruiting phenology transects were conducted throughout the year in deciduous and semi-deciduous forest to determine temporal and spatial variability in resource abundance. Resource use by parrots was evaluated through observations of diet and habitat use. There was significant temporal and spatial variability in food resource abundance, with semi-deciduous forest providing greater food resources for parrots during the dry season, whereas food resource abundance increased in deciduous forest during the rainy season. The critical period of food resource scarcity occurred during May–June at the end of the long dry season. Lilac-crowned Parrots were pre-dispersal seed predators, and exhibited high flexibility in diet, incorporating dietary switching, as well as niche-breadth contraction and expansion, which corresponded with temporal variations in food resource availability. There was low overlap in parrot diets between seasons, with parrots exhibiting a narrow food niche-breadth during the late dry season when resource availability declined. Parrots also demonstrated spatial variation in habitat use, corresponding to fluctuations in the availability of food resources in different habitats. This flexibility in foraging enables parrots to closely track and exploit seed resources which exhibit high temporal and spatial variability in abundance.

No abstract

In seasonally dry tropical forests, tree species can be deciduous, remaining without leaves throughout the dry season, or evergreen, retaining their leaves throughout the dry season. Deciduous and evergreen trees specialize in habitats that differ in water availability (hillside and riparian forest, respectively) and in their exposure to herbivore attack (seasonal and continuous, respectively). We asked whether syndromes of leaf traits in deciduous and evergreen trees were consistent with hypothesized abiotic and biotic selective pressures in their respective habitat. We measured seven leaf traits in 19 deciduous and 11 evergreen tree species in a dry tropical forest in Western Mexico, and measured rates of herbivory on 23 of these species. We investigated the covariance of leaf traits in syndromes related to phenology and associated physiology, and to anti-herbivory defense. We found evidence for syndromes that separated phenological strategies among four traits: toughness, water content, specific leaf area, and carbon:nitrogen (C:N) ratios. We found a trade-off between two other traits: trichomes and latex. Overall, evergreen species exhibited lower rates of herbivory than deciduous species. Lower rates of herbivory were explained by a syndrome of higher toughness, lower water content, and higher C:N ratios, which are traits representative of evergreen trees. Phenology and trait syndromes did not exhibit significant phylogenetic signal, consistent with the hypothesis of evolutionary convergence among phenologies and associated leaf-trait syndromes. Our results suggest that deciduous and evergreen trees could respond to differential water availability and herbivory in their respective habitats by converging on distinct leaf-trait syndromes.Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp.

No abstract

Competition for nest sites by sympatric species can lead to resource partitioning among species. We examined the partitioning of cavity resources by Red‐and‐green Macaws (Ara chloropterus), Blue‐and‐yellow Macaws (A. ararauna), and Scarlet Macaws (A. macao) in the lowland forest of southeast Peru. Red‐and‐green Macaws nested primarily in cavities in emergent Dipteryx trees, and Blue‐and‐yellow Macaws nested predominantly in palm snags. Scarlet Macaws had the broadest nesting niche, and their use of cavities overlapped that of the other two species. These differences in cavity use may be related to differences in size, with Red‐and‐green Macaws the largest of the three species (90 cm long, 1050–1320 g), followed by Scarlet Macaws (85 cm long, 1060–1123 g) and Blue‐and‐yellow Macaws (70 cm long, 1086 g). We did not observe interspecific conflicts between Blue‐and‐yellow Macaws and the other two species. However, Scarlet and Red‐and‐green macaws frequently compete for cavities, perhaps contributing to the use of a wider range of cavity resources by the smaller, less competitive Scarlet Macaws. For the three macaw species combined, 40 of 84 nests (48%) were successful, fledging either one or two young (mean = 1.4 ± 0.43). The overall reproductive output (including failed nests) was 0.60 ± 0.68 fledglings per nesting pair, with no difference between macaw species (P > 0.18). A lack of alternative nest substrates for large macaws may drive resource partitioning by sympatric species, with specialization on either emergent trees or palm snags, whereas less competitive species like Scarlet Macaws need to be flexible and use a variety of nest sites.