Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1982 Gray partridge habitat use and nesting biology in north-central Iowa Vernon Pat McCrow Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Ecology and Evolutionary Biology Commons, and the Environmental Sciences Commons Recommended Citation McCrow, Vernon Pat, "Gray partridge habitat use and nesting biology in north-central Iowa " (1982). Retrospective Theses and Dissertations. 7516. https://lib.dr.iastate.edu/rtd/7516 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. 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Universi^ Micronlms International 300 N. Zeeb Road Ann Arbor, Ml 48106 8224234 McCrow, Vernon Pat GRAY PARTRIDGE HABITAT USE AND NESTING BIOLOGY IN NORTH- CENTRAL IOWA Iowa State University PH.D. 1982 University Microfilms Intsrnâtiona! 300N.zeebRoaa.AmA^or.MI48106 Gray partridge habitat use and nesting biology in north-central Iowa by Vernon Pat McCrow A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY Department; Animal Ecology Major: Wildlife Biology Approved: Signature was redacted for privacy. Signature was redacted for privacy. zhe lAajor Department Signature was redacted for privacy. For the Graduate College Iowa State University Ames, Iowa 1982 ii TABLE OF CONTENTS Page INTRODUCTION 1 LITERATURE REVIEW 4 Taxonomy and Distribution 4 North American Introductions 9 Habitat Use 33 Mobility 49 Social and Reproductive Behavior 51 Population Dynamics 58 STUDY AREA 76 METHODS 84 Capturing and Marking 84 Habitat Use 86 Population Studies 91 Nesting Studies 93 RESULTS AND DISCUSSION 98 Trapping 98 Covey break-up 100 The Marked Sample 101 Age and sex ratios 101 Body weight 102 Necktag-marked partridge 103 Transmitter-marked partridge 105 iii Page Habitat Use 107 Distribution of telemetry observations 107 Distribution of roadside observations 117 Distribution within fields 118 Habitat use by broods 120 Environmental associations 127 Movements and Activity Ranges 136 Sightings of necktag-marked birds 136 Telemetry observations 138 Linear range 143 Activity range in relation to habitat 145 Nesting Studies 148 Nest searching 148 Nest success 149 Clutch size 153 Nest initiation 154 Nest distribution by cover type 155 Vegetative cover at nest sites 159 Nest-site selection in roadsides 168 Comparisons of cover types 172 Population Studies 176 Winter counts 176 Spring-to-fall production and survival 178 Effects of weather on production 180 iv Page Renesting 186 Brood survival 190 Mortality factors 194 CONCLUSIONS AND IMPLICATIONS 198 SUMMARY 204 LITERATURE CITED 211 ACKNOWLEDGMENTS 223 APPENDIX 225 1 INTRODUCTION Perpetuation of wildlife species-populations depends upon the maintenance of habitat to which they are adapted for growth, survival, and reproduction. Changes over time in the quantity and quality of habitat must be within a species' range of tolerance in terms of the ability of individuals to both obtain life requisites (such as food and cover) and compete with individuals of other species (Pianka 1978). Habitat dynamics in agricultural areas are closely tied to land use. Changes in agricultural land use that affect wild­ life populations have occurred in Iowa and other midwestern states following the introduction of exotic game birds in the early 1900s. In Nebraska, Taylor et al. (1978) documented a decline in pheasant (Phasianus colchicus) populations from 1955 to 1976 that was associated with the loss of noncropland areas and a shift in crop types from pasture, hay, and small grains to row crops, with rates of change higher from 1964 to 1976 than from 1955 to 1964. Mohlis (1974) found that similar changes occurred in north-central Iowa from 1938 to 1973, with an increased rate of change since the mid-1950s. A 79% increase in land area planted to row crops from 1939 to 1972 was primarily because of a nearly 10-fold increase in soybean (Glycine max) area, while corn (Zea mays) area increased only 14%. Alfalfa (Medicago sativa) largely replaced other types of hay crops. 2 but the area devoted to all types of hay decreased 56%. Pheasant nesting habitat decreased 44%, with reduced area in oats (Avena sativa), clovers, wetlands, and undisturbed grasslands; winter cover decreased 33%, primarily because of reduced area in farm groves and wetlands. Accompanying these trends in agricultural land use, pheasant populations have decreased in north-central and northwest Iowa since the mid-1960s (Farris et al. 1977). However, gray partridge (Perdix perdix) populations in this region have increased, according to Iowa Conservation Commission harvest estimates and spring and August roadside surveys (Farris and Schwartz 1974). In the Great Plains region of the United States and Canada, gray partridge populations are typically associated with open agricultural land, especially small grain cultiva­ tion interspersed with native grassland or hay and pasture- lands (johnsgard 1973). Occupying the extreme southeastern portion of the species' range in this region, Iowa supports populations of partridge on lands that are dominated by row crop cultivation. Gray partridge were successfully introduced from Europe into north-central Iowa in 1910 (Leopold 1931). Exhibiting relatively little range extension since that time, partridge populations currently occupy most of the northwest quarter of the state (Leopold 1931, Farris and Schwartz 1974). Traditionally, the status of the gray partridge as a game bird in North America has been secondary to that of the 3 pheasant (Johnson 1964). If trends in abundance of these 2 species continue, the gray partridge may replace the pheasant as the primary upland game bird in northern Iowa and in other areas of intensive row crop agriculture; a similar trend in relative abundance of the 2 species has been found in southern Minnesota (Mettler 1977). In an effort to learn more about gray partridge ecology and management potential in Iowa, a 3-year study was initiated in 1975. The objectives of the study were to estimate reproductive effort and success of a partridge population in north-central Iowa, to determine seasonal distribution and movements of a marked seimple of partridge relative to avail­ able habitat types, and to compare partridge use of cover for nesting with that of pheasants. The ultimate goal of this research is to contribute information that can be applied in the management of gray partridge populations for public use and enjoyment. 4 LITERATURE REVIEW Taxonomy and Distribution The taxonomic position of Perdix perdix has been evaluated and summarized by Johnsgard (1973). The species is classified in the order Galliformes, family Phasianidae, subfamily Phasianinae, and tribe Perdicini. Although most commonly known as the gray partridge, other vernacular names include the Bohemian partridge, English partridge, European partridge, Hungarian partridge, Hun, and Hunkie (Johnsgard 1973). The gray partridge is a western Palearctic species; its native range includes western Europe from northern Portugal and central Spain to the British Isles and north to central Scandinavia, east to central Siberia, and south to Turkey and Iran (Dement'ev and Gladkov 1967, Witherby 1941). Within its native range, 10 subspecies are recognized by Witherby (1941), 7 by Dement'ev and Gladkov (1967). P. £. perdix (the central European gray partridge or common partridge) occupies the British Isles and west-central and northwestern Europe. Morphologically, the sexes are similar in general physical appearance. Adults are 30-34 cm long and weigh 375-450 g; females are somewhat smaller than males (Dement'ev and Gladkov (1967)". Females may be distinguished from males by having scapulars and median wing coverts with relatively wide rachis-stripes and 2 to 4 crossbars; males have darker 5 feathers with narrow stripes and no crossbars (Witherby 1941).