KLAMATH COUNTY, OREGON

Transcription

1 Il---~r~n^r Technical Report # LJME;N11'l' POPULATION DENSITY AND HABITAT USE BY RED-NECKED GREBES ON UPPER KLAMATH LAKE, KLAMATH COUNTY, OREGON Oregon Department of Fish and Wildlife Nongame Wildlife Program

2 POPULATION DENSITY AND HABITAT USE BY RED-NECKED ON UPPER KLAMATH LAKE, KLAMATH CO., OREGON GREBES Wedge W. Watkins Oregon Department of Fish and Wildlife Nongame Wildlife Program Technical Report # August 1988 SOUTHERN OREGON UNIVERSITY LIBRARY ASHLAND, OREGON 97520

3 CONTENTS ABSTRACT... 1 INTRODUCTION.. O...O STUDY AREA O METHODS... o... 2 RESULTS AND DISCUSSION o... 2 Population Size and Distribution... 2 Habitat Characteristics RECOMMENDATIONS o.ooooo.oo...ooooo. 5 ACKNOWLEDGMENTS o.o ooo.o...oooo 5 REFERENCES Page

4 POPULATION DENSITY AND HABITAT USE BY REI)-NECKED GREBES ON UPPER KLAMATH LAKE, KLAMATH CO., OREGON Wedge W. Watkins ABSTRACT A survey conducted from May-July 1988 showed that 13 adult Red-necked Grebes (Podiceps grisegena) raised six young on Pelican Bay of Upper Klamath Lake, Klamath County, Oregon. Three broods with a total of seven young were hatched, with one young lost shortly after hatching. Individual nests were not located but a nesting habitat was identified near the mouth of Crystal Creek on Pelican Bay. INTRODUCTION The Red-necked Grebe (Podiceps grisegena) is a common migrant throughout northern California and southern Oregon, but is, a rare nesting species (Bent 1960, Westmore 1965). Its breeding range generally extends from Alaska across western Canada, with populations in northern Washington, Montana, northern South Dakota and Minnesota (Scott 1983). A small breeding population has been reported in the Rocky Point area of Upper Klamath Lake, Klamath County, Oregon since 1960 (Palmer 1962). This disjunct population is the southernmost breeding population known for the Red-necked Grebe in North America. Red-necked Grebe populations have been declining over most of the bird's range due to habitat loss and pollution (Terres 1980). However, very little is known about the status of the Upper Klamath Lake population. The objective of this study was to establish baseline information on the size and distribution of this unique population

5 STUDY AREA The study area was primarily a portion of Upper Klamath Lake near Rocky Point known as Pelican Bay (Figure 1). This area was selected for study on the basis of historical data (Opp, pers. comm.). Pelican Bay is sheltered from the winds and weather associated with most of Upper Klamath Lake. The marsh surrounding Pelican Bay provides excellent nesting habitat for a variety of waterfowl. The water in this area appears to be clearer and cooler than other portions of the lake. Pelican Bay features an abundance of aquatic vegetation with pondweed (Potamogeton sp.) and waterweed (Elodea sp.) being the most common. The density of this vegetation varies with water depth. These aquatic plants harbor large numbers of aquatic insects and small fish that are the primary source of food for the red-necked grebe (Jewett 1953). METHODS The study was initiated on 21 May Nine separate trips were made to Pelican Bay over an eight week period, with a total of 20 observer days used to record information. Observations were made from canoe or boat using binoculars, a spotting scope and a 35 mm camera with a 300 mm lens. RESULTS AND DISCUSSION Population Size and Distribution Thirteen adult Red-necked Grebes were observed using Pelican Bay during the nesting season. Three adult grebes arrived on 11 May (Holland, pers. comm.) and the numbers gradually increased until a total of 13 was observed on 14 June The primary area of use was within 0.5 miles of the mouth of Crystal Creek (Figure 1). As the nesting season progressed, the area of use became more well defined. During nest tending and shortly after hatching, grebe use was confined to within 400 m of a canal opposite the mouth of Crystal Creek

6 Rec 4i p I I.M = ALL. :1..L~ -' _X _- _ ' ' -Z -, -,.. _- 36 J L , I J1 at._-. _. 1'"._. - _ -1L- - ' A..~ is Iu:,#._-( U I K L If "'. L I / / / N 45176,z,. 4V 2 5' 1 a 121, 050 Z' 23 It 'I /'I 4. I -L 1_ J,' 1 6 PRIMARY USE AREA NESTING HABITAT Figure 1. Primary use area of Red-necked Grebes at Pelican Bay, Upper Klamath Lake, Klamath County, Oregon

7 The adult birds did not appear to be closely associated as pairs prior to nesting. This, coupled with the dense marsh vegetation and the secretive nature of nesting grebes, made finding a nest very difficult. Red-necked Grebe nests are composed of floating mats of rotting vegetation attached to reeds and other emergent vegetation. While no nests were located, adult grebes were observed moving in and out of the marsh at specific locations, presumably in close proximity to nest sites. Three broods with a total of seven young were observed shortly after hatching. Two of the family groups had two young; the other group had three young. The clutch size is usually four or five eggs with two to four young being most common (Headstrom 1970). After several days of high wind and increased boating activities on the July 4th weekend, two family groups with three young were observed. Apparently, one of the young birds was lost, and the family groups were mixed. The two families with three young were observed for the remainder of the study. During-the first week after hatching, the young grebes were observed riding on the adults' backs. They are fed aquatic insects and some plant material. The young birds grew at a rapid rate and by the second week after hatching, they were swimming and diving with the adults. After the second week, the family groups began to use more of the Pelican Bay area. Nonbreeding adult birds had a much wider range, but were more common in the area of Pelican Bay near Crystal Creek. Habitat Characteristics Pelican Bay is bordered on the north and south by marsh which provides excellent nesting habitat and escape cover for young birds. The water in this portion of Upper Klamath Lake tends to be clearer and cooler than most of the lake and supports an abundance of aquatic vegetation. This vegetation harbors large numbers of aquatic insects that are a critical food item during the first weeks of a young grebe's life (Bent 1960). The vegetation also provides a food source and shelter for several fish species eaten by the grebes. Rednecked Grebes were observed feeding on fathead minnows, blue chub and yellow perch. Tui chub, Lost River sucker, shortnose sucker, slender sculpin, -4 -

8 marbled sculpin, Klamath speckled dace and rainbow trout are also found in Upper Klamath Lake. However, I believe that size and availability are more important to the grebes than species. Fish become increasingly important to the Red-necked Grebe after the first week of life, and make up to 50-75% of an adult birds' diet (Palmer 1962). RECOMMENDATIONS Red-necked Grebes are nesting successfully on Upper Klamath Lake. Past observations indicate that a small population has been breeding here for several years (Opp, pers. comm.). The birds have never been observed on Pelican Bay in great number, but the population appears to be stable. Habitat unique to this portion of Upper Klamath Lake, i.e., water quality, abundant food supply, adequate nesting habitat and escape cover, appear to be attracting birds to an area outside of their normal range. I recommend that these birds be considered in any management decisions made regarding the aquatic habitat of Pelican Bay and the adjacent marsh. Further study is needed to determine the habitat requirements of these uncommon residents. ACKNOWLEDGMENTS I would especially like to thank Mark Holland, Cindy Lewis, Mike and Peggy Hanson, Dave and Brenda Roskos, and Fred Garmire for their observations and the use of their equipment. I would also like to thank Ralph Opp and John Fortune for their advise on observation methods, species identification and project development. This study was funded by the Nongame Fund administered by the Oregon Department of Fish and Wildlife. - 5-

9 Bent, A.C Headstrom R Jewett S.G REFERENCES Life histories of North American water birds. A complete guide to nests in the U.S. Birds of Washington State. Palmer, R.S Handbook of North American birds. Vol. 1 Loons through Flamingos. Scott, S.L. ed North America. Taverner P.A Terres J.K Westmore A National Geographic Society field guide to the birds of Birds of Western Canada. The Audubon Society encyclopedia of North American birds. Water prey and game birds of North America. -6= -