Anthropogenic pressure on coral reef ecosystems has increased the need for effective restoration and rehabilitation as a management tool. However, quantifying the success of restoration projects can be difficult, and adequate monitoring data are scarce. This study compared growth rates over a six-year period of three Caribbean coral species, staghorn coral (Acropora cervicornis), elkhorn coral (Acropora palmata), and thick finger coral (Porites porites), transplanted on an artificial reef off Maiden Island, Antigua, to literature values for the same species growing on naturally formed reefs in the Caribbean region. The average growth rate of staghorn coral was considerably lower than growth rates reported in the literature, while elkhorn and finger corals showed growth rates similar to literature values. The observed inter-and intraspecific differences may be caused by species-specific growth requirements and/or restoration site conditions, factors that should be taken into account when planning future projects involving coral transplant or rescue. This study also determined the analytical precision of a 'low tech' monitoring method using a basic underwater digital camera and the software program ImageJ to measure growth rates of corals. Measurement error between volunteer analysts receiving only minimal training was shown to be very small, ranging from 0.37-1.40% depending on the coral species. This confirms the validity of this basic technique, particularly in cases where data are sparse and resources for monitoring are extremely limited.
Aim The brown-headed cowbird is an obligate brood parasite known to exploit a large number of host species and use a variety of habitats. Much attention has been directed towards uncovering the fundamental factors that affect cowbird abundance; however, no study has evaluated these factors in the context of a biogeographic-scale analysis that takes into account spatial autocorrelation. Our primary objective was to compare the relative influence of geography, land cover and host species on the local abundance of cowbirds.Location Great Plains region of the USA.Methods We used data from the North American Breeding Bird Survey and the National Land Cover Database to examine the relationships between cowbird abundance and host species, land cover composition and geographic location of a survey route. Multiple regression models were developed for various combinations of these factors. To control for spatial autocorrelation, we used SAM 4.0 (Spatial Analysis in Macroecology) software to implement simultaneous autoregressive modelling of the error term. We then used a model comparison approach to identify the factors that most influence cowbird abundance.Results Among all models examined, host species richness was the single most strong predictor and the sole statistically significant predictor. Cowbird abundance increased with host species richness but did not change in any significant way with non-host passerine richness or abundance of host species. Models with land cover variables tended to have the poorest fit to the cowbird abundance data.Main conclusions Our results suggest that cowbirds may be attracted to areas with greater host richness and/or recruit better in such areas, although our data did not allow direct examination of either process. In a greater context, our study demonstrates the utility of a spatially based and geographically extensive analysis in finding range-wide factors that affect the local abundance of a species.
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