62 SHORTCOMMUNICATIONS VOL. 22, NO. 2

J. Raptor Res. 22(2):62 ¸ 1988 The Raptor ResearchFoundation, Inc.

GREATHORNED (Bubo virginianus) NESTING IN A GREAT BLUE ( herodias)HERONRY

GARY BURKHOLDER AND DWIGHT G. SMITH

From 1981-1987 we studied nesting ecologyof Great site selectionby owls occursin February, shortlybefore Blue (Ardeaherodias) at a heronrylocated at Knox Great Blue Herons arrive; thus, the owls usurp the nest Lake, Knox County, Ohio. Knox Lake was created in of their choice.Incubation dates ranged from 5 March-7 1955 for flood control, and the heronry was locatedin the April, while earliestdates in which youngwere found in remainsof a mixed mesophyticwoodland which was de- nestswere 1 April-7 May. Earliestobserved fledging date stroyed following flooding. Standing trees were leafless was 8 May but youngtypically fledgedin late May or and in various stagesof decay. In 1981, 1982, 1983 and early June. Comparatively,herons arrived in late Feb- 1984 Great Horned Owls (Bubovirginianus) used heron ruary and early March and apparentlyselected and began nest sitesfor breeding.Herein we report our observations to repair nestsshortly thereafter. Heron eggswere laid in of Great Horned nest site selection,breeding chro- late March and early April and youngwere in the nest nologyand reproductiveefforts within the heronry. from late April throughJune and sometimesJuly. Great Horned Owls used nestsconstructed by Great GreatHorned Owl nestsaveraged 2.5 young/nest(range Blue Herons in previousyears: nest bowls contained feath- one-three)but in 2 of the 4 yrs youngdid not fledge.In ers but were otherwise unaltered. All nests used were in both years disappearanceof the 2-3-wk-old young oc- treeslocated in the interior of the heronry.Typically each curred during a period of severestorms and associated tree containedfrom two to sevennests placed at varying high winds. heights; Great Horned Owls used nestslocated in the Although infrequently reported,the use of heron nests middle of the remaining limbs of the dead trees while by Great Horned Owls is apparentlywidespread: Bent Great Blue Herons occupiednests in the upper limbs of (U.S. Natl. Mus. Bull. 170, Pt. 2, 1938) recordedowl use trees but did not use nestsbelow or adjacentto an active of nestsof largerherons in Canadaand the easternUnited owl nestuntil the owletsfledged or the nestwas deserted. Statesand Black-crownedNight Heron (Nycticoraxnyc- Minimum observed distances between active heron and ticorax)nests in California. In central Utah we have found owl nests were about 2 m. In 1982, 1983 and 1984 bothGreat HornedOwls and Long-earedOwls (Asiootus) herons occupiedand repaired severalof the unusedad- nestingin a heronry alongthe western jacent and lower nestsafter owls had departed the nest edgeof Utah Lake, Utah County, in 1969 and 1982. tree area. Reluctance to use nests near active owl nests may have been influencedpartly by the behavior of the ScienceDivision, Mount Vernon Nazarene College, youngowls, which usuallyleft the nestat 2-3 wks of age Mount Vernon, OH. Address of second author: Bi- to move about on adjacentlimbs. ology Department, Southern Connecticut State Although not actually observed,backdating (Anderson University, New Haven, CT 06515. and Hickey, WilsonBull. 82(1):14-28, 1970) from the time young were first recordedin the nestssuggests that nest Received12 November1987; accepted21 April 1988