Date of Award

5-2008

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biology

Abstract

Few studies have focused on golden eagles nesting in North Dakota. This project investigates the ecology of, and the potential effects from energy development on, nesting golden eagles in North Dakota, by collecting historical data, conducting nest checks and surveys (2002-2006).

Historical information was not sufficient for population estimates. Nest checks/surveys indicated that nest densities, occupied nest sites and territories was greatest near the riparian river bottoms. There were 176 potential extant territories. The average minimum distance between occupied nest sites was 6.32km (7.20km to 3.85km). The mean territory area was 8.95 km2 (SD = 4.25 km2, min = 3.09 km2, max 26.65 km 2). With a detection rate of 48.58%, nest surveys revealed 388 nest sites, of which 51 were occupied. Nests on cliffs with a SE, S, SW orientation were found more commonly than tree and ground nests.

Occupied nests ranged from 15 to 50, (2002-2006), averaging 0.81(SD = 0.65) - 1.30 (SD = 0.45) fledglings/nest. One to three chicks were fledged. Twenty-three mortalities were recorded, all juveniles. Wind storms and West Nile were the main causes. Eight of the 18 tagged birds survived.

I observed group hunting by pairs of adult golden eagles. In 2003 I observed 8 separate groups of three or four, in 2004 two groups of 4, and in 2003 and 2005, a group of six was observed.

The "best fit" model, with a significance of 0.10, for both forward selection and backward elimination resulted in selection of the explanatory variables: Slope, Large Tree Woody Habitat, Cropland, Erodibility, Native Prairie, and Aspect with an AIC value of 365.71. Slope (SL), Large Tree Woody Habitat (LW), Cropland (C), Erodibility (Kf), and Native Prairie (NP), were the most parsimonious predictors; (βSL = 0.1693, SE = 0.0131; β LW = -0.1322, SE 0.0288; βC = -0.0581, SE = 0.0131; β Kf = 1.2168, SE = 0.3396; βNP = -0.0212, SE = 0.0105. The categorical variables Aspect had weak correlations yet collectively they met the 0.10 significance level and increased the AIC value for model selection. The results from the habitat suitability map identify areas of high priority for the protection of nesting golden eagles.

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