Agricultural destruction of Northern Pintail nests on cropland in prairie Canada

Abstract

ABSTRACT. It has been postulated that the decline of the Northern Pintail (Anas acuta) population is related to the propensity of female pintails to nest in cropland. Using spatial modeling at multiple scales, we estimated that the long-term average breeding population of Northern Pintails in prairie Canada would have initiated a mean of 974,260 nests/year, of which 47% (457,900 +/-43,270) would have been in cropland. Nest success rates are very low (5%) in spring-seeded cropland with predation and agricultural activity responsible for approximately 78% and 22% of the nest loss, respectively. We estimated that a long-term mean of 94,750 (+/-19,680) nests representing 524,725 pintail eggs would have been destroyed by agricultural seeding and tillage operations on cropland annually. The number of nests/eggs lost in any given year would vary by an order of magnitude dependent primarily upon the size of the pintail population nesting on the prairies in that year. Our estimate of incidental take is quite robust because it is based on multiple, long-term studies using data from across the Canadian prairies. Our analysis provides additional support for the theory that the pintail's habit of nesting in cropland is the probable reason for the decline in the pintail population, irrespective of the cause of nest loss. Although predation is the primary cause of the loss of pintail nests in cropland, the proportion of nests lost to predation in cropland is similar to that in other upland habitats on the prairies. Thus the additional loss from agriculture could well be incremental and may be the proximate causative factor in the pintail population's decline and failure to recover in recent decades. Destruction de nids de Canard pilet causée par l'agriculture sur les terres cultivées des Prairies canadiennesRÉSUMÉ. Une des raisons avancées pour expliquer la diminution de la population de Canard pilet (Anas acuta) est en lien avec la propension des femelles à nicher sur les terres cultivées. Au moyen de modélisation spatiale à de multiples échelles, nous avons estimé que la population nicheuse moyenne de longue date de Canard pilet des Prairies canadiennes aurait initié une moyenne de 974 260 nids/année, dont 47 % (457 900 +/-43 270) se seraient trouvés sur les terres cultivées. Le taux de succès des nids est très faible (5 %) sur les terres à culture de printemps, où la prédation et les activités agricoles sont responsables de 78 % et de 22 % des pertes de nids, respectivement. Nous avons estimé qu'une moyenne de 94 750 (+/-19 680) nids équivalant à 524 725 oeufs de pilets auraient été détruits annuellement par les opérations de travail du sol et d'ensemencement sur les terres cultivées. Le nombre de nids/oeufs détruits au cours d'une année donnée variait d'abord en fonction de la taille de la population de pilets nichant dans les Prairies cette année-là. Notre estimation de la prise accessoire est assez fiable parce qu'elle est fondée sur de multiples recherches de longue date utilisant des données provenant des Prairies ca...

Linking landscape-scale conservation to regional and continental outcomes for a migratory species

“…9 M hectares of idled cropland (summer fallow) to continuous spring-seeded cropland under minimum tillage, has occurred over the past three decades 47,48 . The resultant increase in availability and use of spring-seeded versus idle cropland for nesting is the likely driver of declining reproduction levels 49,50 . At the observed level of annual funding for waterfowl habitat conservation ($31.3 M yr −1 ), it would take >100 years to cover the cost of habitat conversion ($35.7B) needed to achieve a predicted population size meeting the NAWMP goal of 4 M pintails.…”

“…This study also found that productivity was negatively correlated with agricultural intensification at the subregional scale. Indeed a growing body of evidence from North America suggests that the decline in abundance of the pintail, a species that readily nests in residual crop stubble prior to seeding, may be linked to the increase in conservation tillage practices that reduce the availability of undisturbed stubble provided by fallowed cropland 49,50,108 . The economic value of birding and hunting associated with pintails in North America is estimated at >$100 M (2014 USD) annually 10 .…”

“…Modeling frameworks have been developed for predicting outcomes of habitat management for pintails at landscape to regional scales 49 and regional to continental scales 19 . In addition, methods are emerging for explicitly quantifying the sources and patterns of funding for conservation of wildlife habitat in North America 57 .…”

“…Canada's (AAFC) 2016 annual, 30-m crop raster (http://open.canada.ca/data/en/dataset/ba2645d5-4458-414d-b196-6303ac06c1c9) to estimate landscape composition in 2016 for eight habitat classes (spring-seeded cropland, fall-seeded cropland, idle grassland, grazed grassland, hayland, wetland, trees/shrubs, and other). Because wetlands are poorly captured in AAFC's crop mapping layer, we recalculated base habitat composition after including estimated wetland habitat area from the CanVec hydrology layer 116 after adding small wetlands missed by the AAFC and CanVec layers 49 . This approach yielded the 2016 land-cover map for modeling pintail distribution and reproduction throughout the PPR.…”

“…To conduct the spatial analysis, we used ArcGIS version 10.4 (Environmental Systems Research Institute, Redlands, California, USA). Detailed methods for developing the land-cover map are provided elsewhere 49 .…”