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Reproduction and Survival of Radio-Marked Hen Ring-Necked Pheasants in Illinois

1983; Wiley; Volume: 47; Issue: 2 Linguagem: Inglês

10.2307/3808509

1937-2817

Richard E. Warner, Stanley L. Etter,

Animal Nutrition and Physiology

Reproductive success and survival rates were determined for 26 radio-marked hen pheasants (Phasianus colchicus) in east central Illinois during breeding seasons spanning 1972-80. Reproductive success (during either incubation or brood-rearing) or survival beyond 3 months was unlikely for hens equipped with radio packages weighing >27 g. Longevity declined exponentially as the ratio of package weight : body weight increased over a range of 2.3-3.3% for 15 hens radio-marked either prior to incubation or during brood-rearing. We concluded that (1) the radio-marked cohort experienced lower survival rates than normal hen pheasant populations, (2) longevity decreased with increased radio-package weight, and (3) package weight should not exceed a minimum necessary to ensure battery life over the course of the intended study. J. WILDL. MANAGE. 47(2):369-375 Attempts to monitor avifauna have typically included radio packages weighing from 1.3 to 12.5% of a bird's body weight (Brander and Cochran 1969:97). The abandonment of nests or broods by radiomonitored hen pheasants and grouse (Tetraoninae) has been documented by Kuck et al. (1970), Carter (1974), Warner (1975), and Maxson (1978). Radio packages have also been cited as potential agents in the mortality of monitored birds (Hessler et al. 1970, Schladweiler and Tester 1972, Dumke and Pils 1973, Maxson 1978, Erikstad 1979, Johnson and Berner 1980). Despite these findings, radiotelemetry has been used to make inferences about mortality in wild populations. Cochran (1980: 515), in reviewing inferences made from radiotelemetry studies, observed Many species 'seem' to tolerate packages that are 4% of body weight and 'appear' to behave 'normally' not 'too long' after such a package has been harnessed. However, little information exists on how variation in radio-package weights may influence reproduction and survival for a given species. From 1972 through 1980, 26 hen pheasants were radio-marked near Sibley, Illinois to monitor movements and habitat preferences of their broods. Most radiomonitored hens did not provide brood-related data following capture because of aberrant reproductive behavior, mortality, or both; partial radio failure was sometimes a contributing factor. The objectives of this paper are to report reproductive success and survival of wild radio-marked hen pheasants relative to body weight, radio-package weight, and stage of incubation at time of capture. We thank the following staff of the Illinois Natural History Survey for assistance: W. W. Cochran provided technical help and reviewed the manuscript, W. R. Edwards and G. C. Sanderson provided supervisory and editorial support, and E. Steger edited the manuscript. The Max McGraw Wildlife Foundation provided support for the project. STUDY AREAS AND METHODS Radiotelemetry studies were in Ford and McLean counties on the Sibley Study Area (SSA, 1972-74) and on the nearby ' A contribution of Illinois Federal Aid to Wildlife Restoration Project W-66-R, the Illinois Natural History Survey, the Illinois Department of Conservation, and the U.S. Fish and Wildlife Service cooperating. J. Wildl. Manage. 47(2):1983 369 This content downloaded from 157.55.39.104 on Sat, 18 Jun 2016 05:31:47 UTC All use subject to http://about.jstor.org/terms 370 SURVIVAL OF RADIO-MARKED PHEASANTS * Warner and Etter Table 1. Characteristics of hen pheasants radio-marked near Sibley, Illinois, 1972-80. Weight (g) Body/ ReproIncubaReproWeek of package ductive tion ductive Survival Hen capturea Bodyb Package ratio (%) stagee (days) successd (days)e Cause of mortalityf 01 26 889.0 17.6 1.98 I 16 1 111 Predation-probably cat 02 26 866.4 16.1 1.86 I 21 1 104 Unknown 03 26 861.8 26.4 3.06 I 13 1 378 Predation-probably cat 04 26 884.5 25.4 2.87 I 6 0 371 Predation 06 30 911.7 19.5 2.14 I 7 0 90 Unknown 33 26 90 Unknown 35 28 <27 I 21 1 22 Predation-probably cat 40 31 <27 B 0 30 Unknown a Week 1 = 1-7 Jan, week 19 = 7-13 May, week 30 = 23-29 Jul, etc. b Mean weights of hens captured during pre-incubation (1,055 g), incubation (883 g), and brood-rearing (854 g) are nearly identical to weights reported by Anderson (1972:476-477) for hens captured in east central Illinois during the same intervals. c At time of capture, I = incubation, B = with brood, PI = pre-incubation. d Success = 1 if radio-marked hen completed or resumed a given stage of reproduction following capture; 0 if the hen curtailed nesting or failed to resume brood-rearing activities. e Estimates of survival are ? -7 days. f Predation is noted when evidence of predators (scat, dens, tooth marks, etc.) was observed with the remains; actual death by predation was not documented. Ford County Management Unit (FCMU, 1975-80). Pheasant populations have been studied on the SSA for over 30 years (Robertson 1958, Warner 1981). The FCMU was established in 1968 as a pilot study of developed roadside habitat for nesting pheasants (Joselyn and Tate 1972, Warner and Joselyn 1978). Hen pheasants were captured and radiomarked during one of the following phases of reproduction: pre-incubation (captured in May by nightlighting), incubation (captured on the nest in Jun or Jul), or brood-rearing (captured in late Jul or Aug by nightlighting). Labisky (1959) described the nightlighting capture technique and Warner (1979) described the capture of hens incubating eggs. When possible, the following data were collected at the time of capture: age of hen by the proximal primary method (Greenberg et al. 1972), weight of hen, and age and number of chicks or (for incubating hens) the clutch size and stage of incubation. Stages of incubation were determined by flotation (Westerkov 1950) to avoid sacrificing eggs from clutches under study. The weight of the harnessed radio package was recorded for each hen (Tables 1, 2). J. Wildl. Manage. 47(2):1983 This content downloaded from 157.55.39.104 on Sat, 18 Jun 2016 05:31:47 UTC All use subject to http://about.jstor.org/terms SURVIVAL OF RADIO-MARKED PHEASANTS * Warner and Etter 371 Table 2. Statistics for 26 hen pheasants captured during reproduction and radio-marked near Sibley, Illinois, 1972-80.