Tree cavity use by Chimney Swifts: implications for forestry and population recovery

Chimney Swifts used at least 13 different deciduous and coniferous tree species. All of the trees were greater than 0.5 m diameter at breast height (DBH) and were described as hollow or having cavities. Nest or roost tree height was 12.7 ± 7.0 m (mean ± SD; range: 3.6-28.0 m; n = 25) and DBH was 1.0 m ± 0.5 m (range 0.5-2.1 m; n = 21). According to our description of used trees, the number of suitably hollow Chimney Swift nest or roost trees may be two to three times higher, although still rare, in most unlogged compared to logged hardwood forests. Whether the current total supply of suitable nest or roost trees is sufficient to carry the anticipated increase in use by Chimney Swifts as chimney habitat is modified or deteriorates is unknown. Monitoring the frequency of use of tree cavities by nesting and roosting Chimney Swifts over time, and more robustly quantifying the availability of suitable tree cavities in different forest types for nesting and roosting Chimney Swifts, particularly in unlogged versus logged forests, are fruitful areas for future research. . D'après la description des arbres occupés, le nombre d'arbres creux convenables pour la nidification ou le repos du Martinet ramoneur pourrait être de 2 à 3 fois plus élevé -quoique ces arbres sont quand même rares -dans la plupart des forêts de feuillus non-récoltées, comparativement aux forêts récoltées. Nous ne savons pas si la quantité actuelle d'arbres propices est suffisante pour satisfaire l'utilisation accrue anticipée par les Martinets ramoneurs vu la détérioration ou la destruction des cheminées. Le suivi temporel de la fréquence d'utilisation des cavités d'arbres par les martinets pour y nicher ou y dormir et une meilleure quantification de la disponibilité de cavités d'arbres propices dans différents types de forêts, en particulier les forêts intactes versus récoltées, sont des avenues de recherche prometteuses. Utilisation de cavités d'arbres par le Martinet ramoneur : incidence sur les plans de l'exploitation forestière et du rétablissement des population

The impact of waterfowl herbivory on plant standing crop: a meta-analysis

Waterfowl can cause substantial reductions in plant standing crop, which may have ecological and economic consequences. However, what determines the magnitude of these reductions is not well understood. Using data from published studies, we derived the relationship between waterfowl density and reduction in plant standing crop. When waterfowl density was estimated as individuals ha−1 no significant relationship with reduction in plant standing crop was detected. However, when waterfowl density was estimated as kg ha−1 a significant, positive, linear relationship with reduction in plant standing crop was found. Whilst many previous studies have considered waterfowl species as homologous, despite large differences in body mass, our results suggest that species body mass is a key determinant of waterfowl impact on plant standing crop. To examine relative impacts of waterfowl groups based on species body mass, a measure of plant biomass reduction (Rs) per bird per hectare was calculated for each group. Comparison of Rs values indicated some differences in impact between different waterfowl groups, with swans having a greater per capita impact than smaller-bodied waterfowl groups. We present evidence that this difference is linked to disparities in individual body size and associated differences in intake rates, diet composition and energy requirements. Future research priorities are proposed, particularly the need for experiments that quantify the importance of factors that determine the magnitude of waterfowl impacts on plant standing crop

Assessing year‐round habitat use by migratory sea ducks in a multi‐species context reveals seasonal variation in habitat selection and partitioning

Long-distance migration presents complex conservation challenges, and migratory species often experience shortfalls in conservation due to the difficulty of identifying important locations and resources throughout the annual cycle. In order to prioritize habitats for conservation of migratory wildlife, it is necessary to understand how habitat needs change throughout the annual cycle, as well as to identify key habitat sites and features that concentrate large numbers of individuals and species. Among long-distance migrants, sea ducks have particularly complex migratory patterns, which often include distinct post-breeding molt sites as well as breeding, staging and wintering locations. Using a large set of individual tracking data (n = 476 individuals) from five species of sea ducks in eastern North America, we evaluated multi-species habitat suitability and partitioning across the breeding, post-breeding migration and molt, wintering and pre-breeding migration seasons. During breeding, species generally occupied distinct habitat areas, with the highest levels of multi-species overlap occurring in the Barrenlands west of Hudson Bay. Species generally preferred flatter areas closer to lakes with lower maximum temperatures relative to average conditions, but varied in distance to shore, elevation and precipitation. During non-breeding, species overlapped extensively during winter but diverged during migration. All species preferred shallow-water, nearshore habitats with high productivity, but varied in their relationships to salinity, temperature and bottom slope. Sea ducks selected most strongly for preferred habitats during post-breeding migration, with high partitioning among species; however, both selection and partitioning were weaker during pre-breeding migration. The addition of tidal current velocity, aquatic vegetation presence and bottom substrate improved non-breeding habitat models where available. Our results highlight the utility of multi-species, annual-cycle habitat assessments in identifying key habitat features and periods of vulnerability in order to optimize conservation strategies for migratory wildlife