DOI: 10.5061/dryad.pg4f4qrzt
title: Mallards have been replacing Black Ducks in human-altered landscapes in Ontario, 1996-2019

description: The American Black Duck (hereafter Black Duck) has received much attention
 over the years as a popular game bird species that experienced historical
 declines on its wintering grounds. Declines may be due to changes in the
 quality and quantity of breeding habitat, competition with Mallards, or
 both. Although the Black Duck population has stabilized, spatial variation
 in regional population trends of Black Ducks on their breeding grounds can
 provide insight into the relative importance of these alternative
 hypotheses at provincial and local scales. We analyzed indicated breeding
 pairs count data collected in Ontario between 1996 and 2019 through the
 Eastern Waterfowl Survey to evaluate the correlation in breeding densities
 and trends of the five most abundant waterfowl species. We also tested
 whether habitat and anthropogenic disturbance variables could explain the
 distribution of those species. Overall, Mallard breeding pair densities
 increased across the survey area, while Black Duck breeding pair densities
 decreased in the southern and northern part of the survey area but
 remained stable in the central part. Densities of breeding pairs of Black
 Ducks and Mallards were negatively correlated across survey plots but the
 trends in breeding densities were not correlated. Densities of Mallard
 breeding pairs increased in human altered landscapes whereas the density
 of Black Duck breeding pairs was negatively correlated with agriculture.
 Our results suggest that Mallards did not competitively exclude Black
 Ducks on the breeding grounds, but instead, Black Ducks were replaced by
 Mallards following encroachment of agriculture into Black Duck breeding
 habitat. Habitat management plans focused on breeding Black Ducks should
 emphasize reduction in the expansion of anthropogenic perturbations and
 increases in habitat conservation efforts in the central area of the
 breeding range in Ontario.
description: <strong>Waterfowl data<br></strong>The
 waterfowl data have been collected through the The Eastern Waterfowl
 Survey (EWS). A breeding waterfowl survey that has been conducted annually
 since 1990 by CWS in an area extending from northeastern and central
 Ontario east through central and southern Quebec, New Brunswick, Nova
 Scotia, Newfoundland, and southern Labrador. Each spring between
 late-April and early-June, observers counted and identified ducks and
 geese observed on every waterbody, watercourse, and wetland within a
 25-km<sup>2</sup> square survey plot using a
 helicopter. All waterfowl observations were identified
 to species, sex, grouping and numbers (e.g., lone or paired birds,
 flocked, etc.) and georeferenced to a location or waterbody. These
 observations were used to infer the number of Inidcated Breeding Pairs
 (IBPs) according to the standardized method developed by the Black Duck
 Joint Venture for helicopter surveys in Eastern Canada. The full
 methodology for the survey and the IBPs calculatons are described in Helicopter-based waterfowl breeding pair survey in eastern Canada and related studies. <strong>Habitat Variables</strong><br>The wetland habitat availability and landscape disturbance were extracted from the land cover information from the Ontario Forest Resource Inventory (hereafter Ontario FRI; available: https://www.ontario.ca/page/land-information-ontario). The Ontario FRI use imagery acquired from aerial photographs, combined with field validation, to produce digital thematic maps of classified land cover within the boreal-hardwood transition and boreal regions of Ontario.It has a multi-spectral digital orthography resolution of 40 cm and is updated every 10 years, with the most recent update in relation to our study period completed in 2011. We used ArcGIS (ESRI 2014. ArcGIS Desktop: Release 10.2.2. Redlands, CA: Environmental Systems Research Institute) to calculate the area and perimeter of features of biological interest within a 1 km buffer around each plot to account for landscape conditions. <strong>Data<br></strong>The explanatory variables have been scaled for the analysis. The raw data and the scaled data are included. <br><br><strong>Code</strong><br>The R code and Stan code needed to run the model are also included. 
description: # Mallards have been replacing Black Ducks in human-altered landscapes in
 Ontario, 1996-2019
 [https://doi.org/10.5061/dryad.pg4f4qrzt](https://doi.org/10.5061/dryad.pg4f4qrzt) ## Description of the data and file structure ### Files and variables #### File: Acronyms\_Key.csv **Description:**  ##### Variables * Variable name: Identify the acronyms used in the data file * Description: Contain the full name of the species or the landscape variable #### File: habitat\_scaled.csv **Description:**  ##### Variables * numericplot: numeric identifier for each plot * Region: the Region to which the plots have been assigned * aOMS: Proportion of the area in the plot covered by emergent vegetation * aTMS: Proportion of the area in the plot covered by treed wetland * pWAT: Perimeter open waterbodies in kilometers  * aWETL: Proportion of the area in the plot covered by wetlands * pWETL: Perimeter of wetlands in kilometers  * aBUI: Proportion of the area in the plot covered by infrastructure * aAGR: Proportion of the area in the plot covered by agriculture  * aFOR1: Proportion of the area in the plot covered by disturbed forest * ZaOMS: Centered and scaled value for Proportion of emergent vegetation * ZaTMS: Centered and scaled value for Proportion of treed wetland * ZpWAT: Centered and scaled value for Perimeter open waterbodies * ZaWETL: Centered and scaled value for Perimeter wetlands * ZpWETL: Centered and scaled value for Perimeter wetlands * ZaBUI: Centered and scaled value for Proportion of infrastructure * ZaAGR: Centered and scaled value for Proportion of agriculture * ZaFOR1: Centered and scaled value for Proportion of disturbed forest #### File: panel\_id.csv **Description:**  ##### Variables * numericplot: numeric identifier for each plot * Longitude: longitude for the centroid of the plot (in degrees) * Latitude: latitude for the centroid of the plot (in degrees) * BCR: Bird Conservation Region associated with the plot * Panel: Panel rotation for the plot #### File: survey\_1996\_2019.csv **Description:**  ##### Variables * Year: Year the observation were made * numericplot: numeric identifier for each plot * Reg: the Region to which the plots have been assigned * ABDU: indicated breeding pairs for American Black duck * AGWT: indicated breeding pairs for American Green-winged teal * CANG: indicated breeding pairs for Canada goose * MALL: indicated breeding pairs for Mallard * RNDU: indicated breeding pairs for Ring-necked duck ## Code/software The file "ABDU_habitat.R" will run the R code for the American Black duck analysis. The file can be adapted to run the code for the other species. The file "all_sp_correlation_analysis.R" the R code for the multi species analysis. The code for the Stan model is included in the file "correlation_all_sp.stan". ## Access information Other publicly accessible locations of the data: * The Ontario Forest Resource Inventory is available online: [https://www.ontario.ca/page/land-information-ontario](https://www.ontario.ca/page/land-information-ontario) Data was derived from the following sources: * The waterfowl survey comes from the Canadian Wildlife Service Eastern Waterfowl Survey and the landscape variable were extracted from the Ontario Forest Resource Inventory.