Portal de Periódicos da CAPES

Age Determination of Juvenile Spruce Grouse

1975; Wiley; Volume: 39; Issue: 4 Linguagem: Inglês

10.2307/3800243

1937-2817

K. H. McCourt, Daniel M. Keppie,

Turfgrass Adaptation and Management

A technique is described for determining the age of juvenile spruce grouse (Canachites canadensis franklinii). The method is based on measurements of juvenal primaries 7 and 9 and postjuvenal primary 7 obtained from free-living chicks. Age can be estimated on a daily basis up to 75 days of age by measuring only a single feather. J. WILDL. MANAGE. 39(4):790-794 The growth pattern of primary remiges of juveniles has been used successfully as an indicator of age in several galliformes (Bump et al. 1947:84-90, Smith and Buss 1963, Zwickel and Lance 1966, Taber 1969, Schladweiler et al. 1970). With this knowledge researchers can study growth and development of juveniles and timing of reproductive events. This paper presents criteria for age determination of juveniles of the Franklin's race of spruce grouse during summer. Data were gathered during studies at the R. B. Miller Biological Station in southwestern Alberta from 1966 to 1973. Many of the measurements were taken by students employed in the summer assistantship program of the Department of Zoology, University of Alberta, and their help is greatly appreciated. Logistic support was provided by the Fish and Wildlife Division, Alberta Department of Lands and Forests, during 1966 to 1968. D. A. Boag, University of Alberta, provided financial support through his operating grants during the study and gave useful suggestions for improvement of the original manuscript. We thank the University of New Brunswick for aid with publication costs. METHODS Free-living juvenile grouse were captured by hand or with a butterfly net until approximately 10 days of age and later with a snare attached to a telescoping fiberglass pole (Zwickel and Bendell 1967). Juveniles were marked individually by various methods. Lengths of primaries from the tip to the point of insertion in the follicle were measured to the nearest millimeter. Primaries were numbered sequentially from proximal to distal. Sex of chicks could be determined at 35-40 days of age by characteristics of postjuvenal feathers of the ventral pterylae (Ellison 1968) and the postjuvenal upper tail coverts and rectrices (Zwickel and Martinsen 1967). We analyzed measurements of all juvenal and postjuvenal primaries and selected three feathers with which to determine age: juvenal primaries 7 and 9 (J7 and J9) and postjuvenal primary 7 (PJ7). The rationale for selection of the three feathers was as follows. We wished to use measurements of juvenal primaries as long as possible because these feathers show less variation in growth than postjuvenal feathers. Measurements of individual juvenal feathers are very similar at hatching, whereas there is greater variation among chicks of the same age in the time of loss and replacement of juvenal primaries. J7 is the shortest feather present at hatching 'Present address: Renewable Resources Consulting Services Ltd., 11440 Kingsway Avenue, Edmonton, Alberta T5G OX4. Present address: Faculty of Forestry, University of New Brunswick, Fredericton, N.B. E3B 5A3. 790 J. Wildl. Manage. 39 (4):1975 This content downloaded from 157.55.39.27 on Sat, 26 Nov 2016 04:10:00 UTC All use subject to http://about.jstor.org/terms AGING JUVENILE SPRUCE GROUSE * McCourt and Keppie 791 Table 1. Agreement between ages estimated for juvenile spruce grouse from the plotted curve and the known age or that determined from J7 measurements. Age of agreeing within Maximum Prichicks No. deviation mary (days) birds 1 day 2 days (days) J7 0-30 81 86 96 3 J9 15-55 248 65 83 7 PJ7 46-75 99 60 80 7 and grows to the greatest length over the longest period of time. Since J7 could be used to determine age for only 25-30 days, we required measurements of another juvenal primary to extend the period of age determination. Both J9 and J 10 grow until about 55-60 days of age. We chose J9 because it grows to a greater length than J10, thereby providing a more sensitive indicator of age. Finally, to further extend the period of age determination measurements of a postjuvenal feather were needed. PJ7 was chosen because its period of growth overlaps the active period of growth of J9, and it continues to grow rapidly until the grouse is approximately 75 days of age. Hatch dates were known for all chicks for which J7 measurements are presented. All J9 and PJ7 measurements were taken from birds of known age or whose hatch date was estimated from a J7 measurement. Lengths of J7, J9, and PJ7 were plotted against age (Figs. 1, 2, and 3, respectively). A line of best fit from a least squares method was drawn through the plotted points and can be used to estimate age from a given measurement. The accuracy of the growth curve for each feather was evaluated by comparing the estimated age obtained from the curve for a given measurement and the known age (plotted point) of that particular chick. Precision of the growth curves was calculated by determining how close the best estimate of hatch date from J9 and PJ7 was 1s KNOWN AGE MALE 90 FEMALE m SEX UNKNOWN