DOI: 10.5061/dryad.70s5t
title: Data from: Timber harvest and tree size near nests explains variation in nest site occupancy but not productivity in northern goshawks (Accipiter gentilis)

description: Conservation concern for the northern goshawk (Accipiter gentilis)
 reflects evidence that goshawks may abandon nest sites or suffer from
 reduced nesting success in response to some forms of timber harvest.
 However, this evidence is mixed and has yet to be reviewed systemically
 and quantitatively. Therefore, we conducted a meta-analysis to assess the
 extent to which timber harvest and tree size explain variation in goshawk
 productivity and site occupancy. Goshawk productivity was not
 significantly explained by the presence of nearby timber harvest nor by
 the average size of nearby trees either in North America or in Eurasia or
 when averaged across all studies. Effect sizes differed dramatically among
 studies and the average effect size was close to zero (Zr = 0.04).
 However, timber harvest and tree size together more strongly explained
 goshawk occupancy of nest sites or territories. Within studies, goshawk
 nest sites or territories with less timber harvest nearby or relatively
 larger trees were, in most cases, more likely to be occupied. When we
 estimated average effect sizes separately for the two continents, the
 averages were moderate, consistent (Zr = 0.23–0.27), and significantly
 &gt; 0. When we combined studies from North America and Eurasia,
 average effect sizes for timber harvest (Zr = 0.24) and tree size (Zr =
 0.25) were similar in strength and both significantly &gt; 0. Thus
 taken together, our results suggest that although both timber harvest and
 a lack of large trees are associated with lower occupancy by nesting
 goshawks, pairs that nest near timber harvest or in small trees have
 indistinguishable nesting success from pairs nesting in large trees or
 farther from timber harvest. We found substantial heterogeneity in results
 among studies, especially within North America, which is not surprising
 given that studies differed greatly in research methods, forest type, and
 forest management. In conclusion, our results suggest goshawk nest sites
 in populations of conservation concern, such as A. g. laingi, may need
 more protection from timber harvest than they are currently receiving.
 Equally important, to better understand effects of forest management on
 goshawks, we recommend additional studies designed to: (1) better identify
 the spatial and temporal extent of the effect of timber harvest on goshawk
 site occupancy; and (2) determine what goshawks do and where they go after
 a timber harvest.
description: Data for meta-analysis
 derived from studies comparing timber harvest or tree size to nest site
 occupancy or productivity in northern goshawks (Accipiter
 gentilis)These are data derived
 from published literature for a meta-analysis assessing the degree to
 which timber harvest and tree size explain productivity and site occupancy
 in northern goshawks (Accipiter gentilis) We present these data in two
 alternative formats. (A) An Excel spreadsheet with multiple tabs. This
 spread sheet includes many comments linked to individual cells explaining
 the derivation of individual values. (B) A series of .csv files, each
 corresponding to a different tab in the Excel file. These are the same
 data as in the Excel sheet, but without the comments linked to individual
 cells. The Excel tabs / CSV files are as follows: (1) repro_raw These are
 the studies that compared productivity (mostly number of fledged young per
 pair or per nest) to either timber harvest or tree size. We report the
 individual effects reported in each study and our derivation of the
 standard effect size ‘r’. (2) repro_per-study_average For each study
 listed in (1), we have calculated an average effect size (both r and Zr),
 corresponding average sample size (n) and average variance corresponding
 with Zr (vz). (3) occupancy_raw These are the studies that compared the
 occupancy of nest sites or clusters of nest sites to either timber harvest
 or tree size. We report the individual effects reported in each study and
 our derivation of the standard effect size ‘r’. (4)
 occupancy_continent_study_av For each study listed in (3), we have
 calculated an average effect size (both r and Zr), corresponding average
 sample size (n) and average variance corresponding with Zr (vz). (5)
 occupancy_variable_study_av For each study listed in (3), we have
 calculated an average effect size (both r and Zr), corresponding average
 sample size (n) and average variance corresponding with Zr (vz). There is
 only one small difference with (4) above. One of the studies examined the
 correlations between occupancy and both timber harvest history and average
 tree size. Thus for this study, we calculated two average effects on this
 sheet, one corresponding to timber harvest and the other corresponding to
 average tree size. This facilitates comparing effects of tree size to
 effects of timber harvest.Goshawk_Dryad_data_20160322.xlsxrepro_rawThese are the studies that compared productivity (mostly number of fledged young per pair or per nest) to either timber harvest or tree size. We report the individual effects reported in each study and our derivation of the standard effect size ‘r’.repro_per-study_averageFor each study listed in repro_raw, we have calculated an average effect size (both r and Zr), corresponding average sample size (n) and average variance corresponding with Zr (vz).Occupancy_rawThese are the studies that compared the occupancy of nest sites or clusters of nest sites to either timber harvest or tree size. We report the individual effects reported in each study and our derivation of the standard effect size ‘r’.occupancy_continent_study_avFor each study listed in occupancy_raw, we have calculated an average effect size (both r and Zr), corresponding average sample size (n) and average variance corresponding with Zr (vz).occupancy_variable_study_avFor each study listed in occupancy_raw, we have calculated an average effect size (both r and Zr), corresponding average sample size (n) and average variance corresponding with Zr (vz). There is only one small difference with occupancy_continent_study_av above. One of the studies examined the correlations between occupancy and both timber harvest history and average tree size. Thus for this study, we calculated two average effects on this sheet, one corresponding to timber harvest and the other corresponding to average tree size. This facilitates comparing effects of tree size to effects of timber harvest.