Brood Break-up and Dispersal of Ruffed Grouse

Dispersal of juvenile ruffed grouse (Bonasa umbellus) from three broods during the fall of 1964 was studied with radio-telemetry techniques. Results indicate two components to this activity: brood break-up followed by distinct dispersal movement. The break-up period began around 7 September. The individual members of two autonomous broods separated from each other, yet remained near or in their summer brood ranges. Break-up ranges covered by 4 males and 4 females averaged 13.4 and 7.7 acres, respectively. Females displayed a greater affinity for lowlands and adjacent edges, as opposed to upland types, than did the males. Non-sibling congregations of grouse occasionally occurred. On 24 September, 17 days after brood break-up, three grouse began dispersal movements within 5 hours of one another. Activities of five radio-marked grouse during the dispersal period are described, two of them in detail. Photoperiod is suggested as the likely control over the behavior, the trigger for actual egress possibly being an entering weather front. A second dispersal move occurred on 7 October, when two grouse again moved a considerable distance. Climatological conditions were almost identical to those of 24 September. Dispersal movement was observed to be highly unidirectional and rapid. Each emigration from one area to another took place in 4 days of travel time or less. Although extensive open habitat was avoided, all other canopied habitat was quickly traversed. The straight line distances of dispersal averaged 1.85 miles, with a maximum of 3.34 miles for a female. Maximum movement of 5,709 ft per day was recorded, but daily movement averaged 3,019 ft per day. Population figures indicate that this fall shuffle of grouse is independent of population densities. Further, "crazy flight" behavior is explained as the probable manifestation of typical dispersal activity and not symptomatic of some abnormal condition. During late summer and early fall, juvenile ruffed grouse proceed through a behavioral sequence consisting of separation from the brood, eventual dispersal from the brood range, and establishment in a fall range. This has been concomitantly termed "brood break-up" and "dispersal. " Many investigators (King 1937, Fisher 1939, Bump 1 Paper No. 6759 Scientific Journal Series, Minnesota Agricultural Experiment Station, St. Paul, 55101. s er and early fal , juveouse proceed through a bee ce consisting of separation o , eventual dispersal from the , a d establishment in a fall i as been concomitantly termed et al. 1947, Edminster 1947, Chambers and Sharp 1958, Eng 1959, Gullion and Marshall 1960, Hale and Dorney 1963, and Kupa 1966) have noted it from diverse localities. The ruffed grouse is a non-migratory species, yet within its distributional realm, which extends in a broad band across North America where suitable habitat occurs (Aldrich 1963), dispersal occurs. The constant flux of individual genetic backgrounds l. 947, Edminster 1947, Chambers and 1958, Eng 1959, Gullion and Marl 960, Hale and Dorney 1963, and 966) have noted it from diverse loi s. ffed grouse is a non-migratory spe, et within its distributional realm, This content downloaded from 157.55. 39.215 on Wed, 31 Aug 2016 05:18:13 UTC All use subject to http://about.jstor. org/terms 610 Journal of Wildlife Management, Vol. 33, No. 3, July 1969 would ultimately be of importance to the population and the species. Allee et al. (1949:363) feel "that dispersion, along with natality and mortality, can be one of the major factors controlling population growth form and behavior. " Dispersal of individuals, the lowest denominator which brings about dispersion in the population, can have ultimate import upon the perpetuation of the group through increased probability of individual genotypic survival. Dispersal behavior of ruffed grouse has been known for some time but there are few data on the specific activities of individuals. One substantiated factor is that mainly juvenile grouse disperse, (Bump et al. 1947, Chambers and Sharp 1958, Gullion and Marshall 1960, and Hale and Dorney 1963). However, the conventional banding and release methods used by the preceeding investigators did not allow a further insight into the specifics of dispersal activity. Such important information as the timing of separation from the brood, daily movements, directional preferences, habitats traversed, and factors influencing timing or stimulating these behaviors, are poorly known. The development of a radio-telemetry technique (Marshall and Kupa 1963) enabled us to obtain specific data regarding the activities and movements of juvenile grouse during the late summer and fall of 1964 at the Cloquet Forest Research Center, University of Minnesota (Godfrey 1967: 16). The valuable advice, assistance, and constructive criticism of G. W. Gullion is gratefully acknowledged. Our thanks are extended to B. A. Brown, Superintendent of the Cloquet Forest Research Center, for making available the facilities of the Research Center, and to private land owners who extended the use of their property for this research. G. Hermanson, F. J. Svoboda, and R. Wallestad served as field assistants. The electronic abilities of S. L. Markusen were paramount to the success of the project. This project was supported by the National Science Foundation Grant GB-1345 as well as by the Minnesota Agricultural Experiment Station Project 17-83H, Federal Aid to Wildlife Restoration, Minnesota Project W-35-R, and the Minnesota Division of Fish and Game. STUDY AREA AND METHODS The Research Center is located 4 miles southwest of Cloquet in Carlton County, Minnesota, and includes 3,365 acres of land, two-thirds of which are upland forests and the remainder, lowland types. Magnus (1949), Marshall (1958:296), Gullion et al. (1962:617-618), and Gullion and Marshall (1968:119-120) have described the soils, topography, and vegetation of the area. Generally, the lowland areas are characterized by a poorly drained, peat-organic soil, supporting either extensive alder (Alnus rugosa) or black spruce (Picea mariana), balsam fir (Abies balsamea), and larch (Larix laricina) stands with alder edges (nomenclature after Gleason and Cronquist 1963). The well drained, loamy-sand uplands support aspen (Populus spp.), paper birch (Betula papyrifera), white spruce (Picea glauca), and red, white, and jack pine (Pinus resinosa, P. Strobus, and P. Banksiana). Much of the understory on the uplands is dominated by thick hazel (Corylus cornuta) brush. The land bounding the Cloquet forest is made up of woodland, marsh, and open fields, and grouse can move in any direction off the area. Grouse were captured in lily pad traps, and marked with an identifying leg band in the 1900 series (Gullion 1965). The juveniles were equipped with radio transmitters (Brander 1968), released as intact broods, This content downloaded from 157.55. 39.215 on Wed, 31 Aug 2016 05:18:13 UTC All use subject to http://about.jstor. org/terms RUFFED GROUSE BREAK-UP AND DISPERSAL Godfrey and Marshall 611 Table 1. Summary of radio-tracking data on 10 juvenile grouse on the Cloquet Forest Research Center during brood break-up