Long‐term and widespread changes in agricultural practices influence ring‐necked pheasant abundance in California. Issue 8 (15th March 2017)

• Record Type: Journal Article
• Authors: Coates, Peter S.; Brussee, Brianne E.; Howe, Kristy B.; Fleskes, Joseph P.; Dwight, Ian A.; Connelly, Daniel P.; Meshriy, Matt G.; Gardner, Scott C.
• Is Part Of: Ecology and evolution. Volume 7:Issue 8(2017:May)
• Page Start: 2546
• Page End: 2559
• Publication Date: 2017-03-15
• Subjects: abundance -- Annual Game Take Survey -- Breeding Bird Survey -- California -- Christmas Bird Count -- cropland -- habitat loss -- land use conversion -- pesticide -- Phasianus colchicus; Ecology -- Periodicals; Evolution -- Periodicals; 577.05
• DOI: 10.1002/ece3.2675
• Languages: English
• ISSNs: 2045-7758

Abstract

Abstract: Declines in bird populations in agricultural regions of North America and Europe have been attributed to agricultural industrialization, increases in use of agrochemical application, and increased predation related to habitat modification. Based on count data compiled from Breeding Bird Survey (BBS) from 1974 to 2012, Christmas Bird Count (CBC) collected from 1914 to 2013, and hunter data from Annual Game Take Survey (AGTS) for years 1948–2010, ring‐necked pheasants ( Phasianus colchicus ) in California have experienced substantial declines in agricultural environments. Using a modeling approach that integrates all three forms of survey data into a joint response abundance index, we found pheasant abundance was related to the amount of harvested and unharvested crop land, types of crops produced, amount of total pesticide applied, minimum temperature, precipitation, and numbers of avian competitors and predators. Specifically, major changes in agricultural practices over the last three decades were associated with declines in pheasant numbers and likely reflected widespread loss of habitat. For example, increases in cropland were associated with increased pheasant abundance during early years of study but this effect decreased through time, such that no association in recent years was evidenced. A post hoc analysis revealed that crops beneficial to pheasant abundance (e.g., barley) have declined substantially in recent decades and were replaced by less advantageous crops (e.g., nut trees). An additional analysis using a restricted data set (1990–2013) indicated recent negative impacts on pheasant numbers associated with land use practices were also associated with relatively high levels of pesticide application. Our results may provide valuable information for management policies aimed at reducing widespread declines in pheasant populations in California and may be applicable to other avian species within agricultural settings. Furthermore, this general analytical approach is not limited to pheasants and could be applied to other taxa for which multiple survey data sources exist. Abstract : Declines in bird populations in agricultural regions have been attributed to agricultural industrialization and intensification. Using an analytical approach that integrates various forms of survey data over multiple decades into a joint index, we identified specific changes in agricultural practices that have impacted ring‐necked pheasants ( Phasianus colchicus ) abundance. Our results likely will provide valuable information for management policies aimed at reducing widespread declines in farmland bird abundance.