Marbled Murrelet Chick and Eggshell Fragments from Inland Washington

Abstract

A marbled murrelet (Brachyramphus marmoratus) chick and three small eggshell fragments (UWBM 43053) were found on the ground in the Helena Creek drainage 9.5 km south and 2.5 km east of Darrington in Snohomish County, Washington. The chick was found partially decomposed on 27 June 1989; the eggshell fragments were found on 14 July 1989, 1.5 m from where the chick was found. The site is 2.7 km up Helena Creek from its confluence with Clear Creek, or 6.3 km from its confluence with the River. The specimens were found 18 m north of a dry stream bed (about 4 m wide), and 240 m east of Helena Creek; elevation is 594 m. The mouth of the Snohomish River, 45-50 km to the southwest, is the closest salt water. The chick was identified by comparison with a color photograph and descriptions of chicks by Simons (1980) and Binford et al. (1975). The bird was maggoty when found; judging from the size of the larvae, it had been dead for perhaps 4 days. The chick nevertheless retained most of its plumage upon preparation. It was entirely downy, with a wing length (wrist to the end of the down) of less than 25 mm, suggesting that it was less than 3 days old (Simons 1980; Hirsch et al. 1981). Subtracting 30 days for the incubation period (Sealy 1974), we estimate a hatching date of 22-23 June and a laying date of 23-24 May. The three eggshell fragments, the largest of which is 6 mm across, were identified based on their similarity to Kiff's (1981) description of marbled murrelet egg specimens and a comparison with an egg (UWBM 43031) found on Long Island in Pacific County, Washington, in July 1989 (J. Atkinson, pers. comm.). Using Munsell color notation (Anon. 1976), the fragments had a ground color between 5GY 8/4 and 2.5GY 7/4; one had a 7.5Y 7/6 spot, and two were marked with blackish scrawls. These colors closely resemble those of UWBM 43031 and Kiff's descriptions. The chick and eggshell were found in unmanaged forest dominated by western hemlock (Tsuga heterophylla) and western red cedar (Thuja plicata) on a west-facing 30% slope. The overstory was western hemlock and western red cedar with some pacific silver fir (Abies amabilis). The hemlocks were primarily 40-45 cm dbh (diameter breast-height), with an understory of 10-20 cm dbh hemlocks. Canopy closure was 60-65%. The forest understory was comprised of sword fern (Polystichum munitum), devil's club (Oplopanax horridum), Oregon grape (Mahoma oregona), bunchberry (Cornus canadensis), deer fern (Blechnum spicant), huckleberry (Vaccinium sp.), western hemlock and vine maple (Acer circinatum). Tree size in the stand and the presence of scattered large remnant Douglasfirs support the assertion that the area was burned in the large Sauk Prairie fire which occurred around 1825 (Henderson and Peter 1984). The chick and eggshell fragments were found at the base of a western hemlock 23 m high and 41 cm dbh. There was no depression, scrape, droppings or other evidence of a ground nest; furthermore, ground vegetation would make access to a ground nest difficult. The hemlock was heavily infected with dwarf mistletoe (Arceuthobium tsugense), which results in multiple branches at infected sites along the tree limbs (known as witches' brooms). Witches' brooms collect organic material and are often covered with thick blankets of moss. The hemlocks in this part of the drainage were heavily infected with dwarf mistletoe, making witches' brooms common. The hemlock was 3 m from a large remnant Douglas-fir (Pseudotsuga menziesii) about 38 m high and 152 cm dbh. This tree had many large lateral branches covered with moss. The top of the Douglas-fir extended above most of the canopy and projected over the hemlock under which the chick was found. The proximity of the chick and eggshells to the trunk of the hemlock and to each other suggests that they fell from a nest in either the hemlock or the Douglas-fir. This habitat is consistent with that of other marbled murrelet tree nests (Marshall 1988), although the nest may possibly have been in a smaller tree than usual. The western hemlock with witches' brooms could have provided sheltered horizontal moss-covered nest sites like the large limbs on which other nests have been found.