R.E. Johnson 1968 No. 29 Tilden Regional Park, Contra Costa Co., Calif. Overcast, cool, wind from west. 3:30 - 4:30 PM. Two birds circle occasionally, but usually hover facing the wind (i.e. face west) over grassland (grass, dill, mustard, thistle; all mostly dry) west of the main ridge-top. A Sparrow Hawk dove, circled, & harassed one of these birds. The R.T. gradually drifted south along the ridge (ridge is N-S) & the Sp. Hk left it & returned north & out of sight. The two species certainly can't be competing for food but perhaps they do compete for hovering space along a one dimensional foraging ridge such as this one. Usually the two R.T.'s hovered 1/4 mile apart, but now & then they would move closer (50-100 ft.) together & hover briefly, as if coming over to say hello, and then again separating. Once they changed positions along the ridge, the north one then occupying the area of the south one & vice versa. (see notes on March 3, 1967) A Shrike foraged from the top of an isolated bush beneath one bird & paid no attention to hawk above. The hawks disappeared between 4:20 & 4:40 PM. The wind continued but the sun was low & visibility was decreasing rapidly.