Aerial hunting methods have been de- scribed for several species of herons, including the Snowy Egret, Egretta thula (Kushlan, 1972); Louisiana Heron, Hydranassa tricolor (Kushlan, 1972); Great Egret, Casmero- dius albus (Rodgers, 1974); Gray Heron, Ardea cinerea (Marshall, 1961); Great Blue Heron, A. herodias (Hedeen, 1967); and Yellow-crowned Night Heron, Nyctanassa violaced (Panner, 1968). Diving from flight was briefly noted in Little Blue Herons, Florida caerulea, by Dickinson (1947) and Jenni (1969), but has not been described in detail. In the period from late July to September 1972, I observed a total of 162 aerial dives by adult and immature Little Blue Herons during 11 periods of observation at the Welder Wildlife Refuge, San Patricio County, Texas. Such behavior was first noted on 26 July, although I had been studying Little Blue Heron feeding habits since April. Interest- ingly, the tnore typical Wade/Walk Slowly method of feeding (Meyerriecks, 1962) was not often observed during this July-to-Septetnber period. Observations were tnade from a car using a 15-60X spotting scope. The herons dived and caught prey as close as 30 m from me, without indicating awareness of my presence. The sites of obsetw-ation were at Encino and Pollito Lakes on the refuge. During late summer these lakes become covered with an opaque mat of vegetation, consisting of Najas guadalupensis, Heteranthera dubia, and green algae. The herons' activities were primarily at the edges of the lakes in areas of floating lotus (Nelumbo lutea) and tall, entergent grasses (Paspalum spp., Panicurn spp.). Aerial hunting behavior was variable in the herons, but typically it began with the bird flying from an elevated perch out over the lake, frequently banking sharply and emitting loud calls. In contrast to normal flight positioning, the neck was partially ex- tended and the legs dangled. Before diving the heron usually hovered like a tern. The dive was performed feet-first, unless the bird was diving froin five m or higher. In that case the bird plmnmeted head-first, righting itself just above the surface to enter the water feet-first. Frequently there was a last-moment directional change before the bird reached the water. As it contacted the water the heron speared its prey with a normal bill-thrust. If the water was too deep for standing, the bird swash on the surface; if the water was very shallow it might run a few steps as it struck. Hunting flights were usually brief and low, one to three meters above the water, though sometimes a dive was made from up to 10 m. Sel ...... bcr 1974 GENERAL NOTES 281 Vol. 86, 1'/o. 3 Ninety percent of the aerial hunts were accompanied by calls, during flying, hovering, or diving. These calls varied in tone, duration, and pitch, but may be represented as croak or creek. There are several possible functions for the calls. As the heron often made a directional change while diving, I suspect that frogs (the usual prey) might have reacted to the call, leaping as the bird descended. It is possible that such leaping would commit a frog to one direction of escape and iaproves the heroh's chances of in- tercepting it. On the other hand, it has been reported that frogs exhibit "physical im- mobility and reduced responsiveness" when frightened by a noise (Nash et al., 1970; Boice and Williams, 1971). Perhaps the heron can effectively iramobilize some prey by calling. Finally, the calling may also serve a social function, as the same calls typically are given during intraspecific chases about the feeding areas. Often several herons aerial- hunted on the same lake simultaneously, but in such cases they did not feed in close proximity; thus cooperative hunting seems highly unlikely. Of the 25 identified prey items taken by aerial hunting, 23 (92 percent) were frogs (Rana pipfens and/or R. catesbeiana) eight to 13 cm long, and two were small fish. This differs greatly from the diet obtained by Little Blue Herons using the common Wade/ Walk Slowly method. From 4 April to 31 July I recorded 152 captures by the latter technique in adults and juveniles. Sizes estimates of each item, made through compari- son with the heroh's bill, showed the prey to be ahnost entirely fish and crayfish, with a mean body length of slightly greater than two cm. Using a length-weight curve plotted for 60 small fish trapped in the vicinity, I determined that the average prey item taken by wading weighed slightly less than one gram. By contrast, the aerial method resulted in the capture of frogs that were eight to 13 cm long and which weighed considerably more. It was not possible to determine the result of all dives into vegetated areas, but of the 101 "scoreable" dives, 25 (25 percent) were successful in capturing prey. This is a much lower success rate per strike than that attained by the Wade/Walk Slowly method. My data show 152 captures out of 271 strikes (56 percent accuracy) for wading Little Blue Herons, and comparable figures derived from Recher and Recher (1969) show an accuracy of 58 percent. In my data on aerial hunting, adults (dark plumage) were not iound more efficient than juveniles (white plumage)--and as demonstrated by Recher and Recher (1969) for wading hunting; however, my sample size is too small for proper analysis of this aspect. Wading hunting is surely less energy-consuming and more accurate than aerial hunt- ing, but it provides smaller prey. It is not known how much more energy is used in fly- ing, so direct comparison of the overall efficiencies of the two hunting methods is not possible. As aerial hunting was observed only in the late summer, it may involve certain ad- vantages that disappear by late September. Several factors may be important: 1, the tadpoles of Rana pipfens and R. catesbeiana metamorphose in late summer into air- breathing, surface-dwelling adults (thus making a new food source potentially available to the herons); 2, these frogs tend to move into shallower water and generally swim poorly during the metamorphic process (Goodyear and Altig, 1971); 3, the vegetation mat becomes densest at that time of year, hiding the fish and thereby rendering this normal food source less accessible to the herons; 4, the aquatic grasses grow tall enough to render the newly-metamorphosed frogs inconspicuous to a wading but not to a flying heron; and 5, the lotus leaves reach peak development then, providing convenient but vulnerable places for frogs to bask in the sunshine. Aerial hunting was most common during dawn and dusk periods of the day, when frogs are most likely to be warming 282 THE WILSON BULLETIN September 1974 Vol. 86, No. 3 themselves at the water's surface or on the lotus leaves (Brattstrom, 1963). The dis- appearance of aerial hunting in autumn is probably associated with the recession of the various forms of aquatic vegetation, the passing of the frogs from a particularly vul- nerable phase in their development, and/or the frogs' dispersal from the vicinity. Aerial hunting, then, may be a behavioral adaptation for exploiting an ephemeral, large-item food source; or, it may be an alternate strategy that the herons must resort to when their usual food source is temporarily unavailable. During this study ! received financial support from an N.I.H. Training Grant (No. 5 TO1 GM01779) of the Department of Ecology and Behavioral Biology, University of Minnesota, and a research fellowship from the Rob and Bessie Welder Wildlife Founda- tion, Sinton, Texas. Acknowledgment is made to Dr. Frank McKinney (University of Minnesota) for research advice and editorial assistance and to Dr. Clarence Cottam (Di- rector, Welder Wildlife Foundation) for supervision and assistance in the field. LITERATURE CITED BoicE, R. AND R. C. WILLIAMS. 1971. Delay in onset of tonic immobility in Rana piplens. Copeia, 1971 (4) :747-748. BRATTSTROM, B. H. 1963. A preliminary review of the thermal requirements of am- phibians. Ecol., 44:238-255. D1/2I1/2so, J. C. 1947. Unusual feeding habits of certain herons. Auk, 64:306-307. GOODYEAR, C. P. AND R. ALTIG. 1971. Orientation of bullfrogs (Rana catesbeiana) during metamorphosis. Copeia, 1971 (4) :362-364. HZDE, S. 1967. Feeding behavior of the Great Blue Heron in Itasca State Park, Minnesota. Loon, 39:116-120. Jz, D.A. 1969. A study of the ecology of four species of herons during the breed- ing season at Lake Alice, Alachua County, Florida. Ecol. Monogr., 39:245-270. KusInA, J. A. 1972. Aerial feeding in the Snowy Egret. Wilson Bull., 84:199-200. MARSHALL, R. V. A. 1961. Herons fishing from the air. Brit. Birds, 54:202. MEYERRIECKS, A.J. 1962. Diversity typifies heron .feeding. Nat. Hist. Mag., 71:48-59. NASH, R. F., G. G. GALLUP, JR., AND M. K. McCLURE. 1970. The immobility reaction in leopard frogs (Rana piplens) as a function of noise-induced fear. Psychon. Sci., 21:155-156. PARMER, H. E. 1968. Unusual behavior of a Yellow-crowned Night Heron. Migrant, 39:12. RECHER, H. F. AND J. a. RECHER. 1969. Comparative foraging efficiency of adult and immature Little Blue Herons (Florida caerulea). Anim. Behav., 17:320-322. RODCERS, J. A. JR. 1974. Aerial feeding by Snowy and Great Egrets in Louisiana waters. Wilson Bull., 86:70-71. DOUCLAS W. MocK, Department of Ecology and Behavioral Biology, J. F. Bell Museum of Natural History, University of Minnesota, Minneapolis, Minnesota 55455. Accepted 11 4pril 1974.