The Influence of Moonlight on the Behavior of Goatsuckers (Caprimulgidae)

THE INFLUENCE OF MOONLIGHT ON THE BEHAVIOR OF GOATSUCKERS (CAPRIMULGIDAE)

ALEXANDER M. MILLS • Departmentof Biology,Carleton University, Ottawa, Ontario KIS 5B6, Canada

ABsTR•CT.--Whip-poor-wills(Caprimulgus vociferus) showed significantly higher levels of locomotory,vocal, and nestactivity during twilight and bright moonlightthan under moon- lessconditions. Field observationsand nestrecord card data indicated that Caprimulgusspecies usuallysynchronize their reproductivecycle with the lunar cycle.Hatching tends to occur during young waxing moons,presumably so that moonlight-enhancedforaging will be at a maximumwhile the dependentnestlings are an energyburden on the parents.Observations of foraging Whip-poor-wills suggestthey are primarily visually oriented, unlike the bats (Chiroptera). Received26 March 1985,accepted 17 November1985.

MOSTnocturnal flying insectivoresare echo- 1983), as are correction formulae for coordinates. Be- locating bats (Fenton 1974, 1984; Simmons and causelunar light intensity increaseswith increasing Stein 1980), but a significant though unknown %MFI and moon height (Bowden 1973), I grouped proportion (15% by taxa) are non-echolocating nights into 5 categoriesbased on %MFI at midnight (0%, 1-25%, 26-50%, 51-75%, and 76-100%), and then birds, most of which are goatsuckers(Capri- subdivided them based on moon height (below the mulgidae) in the genus Caprimulgus. horizon, 1-100 min above the horizon, 101-200 min Most male caprimulgids are conspicuousby above,and 201-300 min above).Each 30 min during their songs,and many accountshave reported monitoring, I recordedcloud cover and wind strength increased singing in bright moonlight (e.g. basedon a predeterminedsubjective scale of 0-3. Wynne-Edwards 1930, Brauner 1952, Cooper Locomotoryactivity.--Temporal patterns in the lo- 1980, Bjorklundand Bjorklund 1983). This sug- comotory activity of Whip-poor-wills were moni- geststhat goatsuckersare moon-loving or lu- tored by radiotelemetry.The radio packagesworn by narphilic, unlike the insectivorousbats, which the birds as backpacksaveraged 4.9 g. The signals appear to be lunarphobic or lunar-indifferent (173.8-174.1 MHz) were detected with a Merlin 12 (Morrison 1978,Bell 1980,Anthony et al. 1981). (CustomElectronics, Urbana, Illinois) receiver oper- ated with a directional 5-element Yagi antenna. Ef- The purposeof this study was to seeif capri- fective range varied from 500 to 1,000 m, and all mulgids, especiallyWhip-poor-wills (Caprimul- transmitters performed for the entire field season. gus vociferus),adjust locomotory (and hence Eleven birds (7 males, 4 females) were outfitted feeding), vocal,and nest activitiesaccording to with radios. Two males disappearedand 1 female lunar conditions. was found dying from an eye injury a week after being tagged. The 8 remaining birds were each MATERIALS AND METHODS trackedfor 43-63 days.All 5 males held territories and all 3 females and 4 of 5 males fledged young Studysite.--I conductedfieldwork near Rideau Lake while tagged. Narrows (44ø43'N,76ø17'W), eastern Ontario, May- Individual pairs were monitored from blinds near July 1983 and 1984. This was a region of marginal their nests. Readings,taken every 4 min, were de- farmland,forest, rock outcrops, and many smalllakes, fined in terms of distance (near, medium, far), as as- where both Whip-poor-wills and Common Night- sessedby the intensity of the radio signal and the hawks (Chordeilesminor) were common. direction (1 o'clockthrough 12 o'clock).Any change Lunar,solar, and meteorologicalconditions.--Percent- from the preceding reading in distance or direction agesof moon faceilluminated (%MFI), moon heights qualified as a move. In all, 14,782telemetry readings (measured in time), and times of sunrise, sunset, and were taken. various solar positions below the horizon are given I distinguished periods of solar influence (twi- in the AstronomicalAlmanac (e.g. Vohden and Smith light) from periodsof lunar influence(night) by de- termining when moonlight (> 25%MFI) began to influence activity after dusk and ceasedto influence activity before dawn. Presentaddress: Department of Zoology, Univer- Instancesof Whip-poor-will feeding sallies were sity of Guelph, Guelph, Ontario NIG 2W1, Canada. recordedvisually for distanceand direction.

37O The Auk 103: 370-378. April 1986 April 1986] Moonlightand Goatsucker Behavior 371

I could tell when Common Nighthawks were ac- ricanOrnithological Society for C. rufigenaand C. pec- tive from their distinctive flight calls. I divided the toralis;and from Sprunt (1940) and the NANRP for night into 10-min censusperiods beginning at sunset C. carolinensis.For the nighthawks (Chordeilesminor and ending at sunrise(with an adjustmentperiod and C. acutipennis),similar data (74 recordsfrom 29 midway of 0-9 min), and noted whether nighthawks yr) came from the NANRP, the ONRS, the MNRS, were heard in each period. the Prairie Nest Records Scheme, and the Quebec Vocalactivity.--The 5 radio-tracked males contrib- Nest RecordsScheme. These data were pooled by ge- uted equally to songactivity. For each 10-min census nus. period, I noted whether each monitoredmale sang I defined hatching datesin terms of days after the 1-10 "Whip-poor-will" units, 11-100 units, 101-1,000 most recent full moon, and divided the lunar month units, or not at all. These were respectivelyassigned into 10 3-day periods, such that the new and full scoresof 1, 2, 3, and 0. Song counts were made in moon dateswere in the middle of 3-day periods. Pe- 2,865 10-min periods.I usedmovement results to dis- riods, then, are days 2-4, 5-7 ..... 26-28, 29-1. Be- tinguish twilight 10-min periodsfrom night ones. causethe last period is only 83% the length of the I also measuredthe levels of aggressiveresponse others(because the lunar month is actually29.5 days), by male Whip-poor-wills to taped song. Five loca- expectedvalues in the statisticaltests were adjusted tions along a prescribedroute away from the telem- accordingly. etry site were used for solicitation trials. Care was Statisticalanal¾$is.--For each solar-definedand lu- taken to choose quiet times (wind category 0 or 1) nar-defined category,I generatedscores for move- and to spread the 15 test times (3 dusk, 3 dawn, 3 ment (percentageof radio readingsthat were moves), darkness,6 moonlight) over the seasonto prevent singing (percentageof theoretical maximum score), habituation to the tape. and nest departuresand nest feedings (numbers per Eachtrial (n = 75) involved 4 repetitionsof 15 s of 1,000 observationminutes). Birds temporarily out of song played at full volume on a portable cassette range as determined by telemetry and birds on nests player followed by 15 s of silence. A positive vocal were not included in calculating movement and responserequired that the local male sing, and a pos- singing scores.A 2 x 2 contingencytable for solar itive visitationresponse required that the male either and lunar conditionsdistinguished twilight periods fly over the tape or land within about 10 m. A bird from night periods. could respondafter the 1st, 2nd, 3rd, or 4th 15-spre- Night scoreswere subjectedto multiple regression sentation (or never), scoring 4, 3, 2, or 1 (or 0), re- and correlation analysisusing dummy variables for spectively. the various categoriesand weighted according to Becausesong tempo (the number of "Whip-poor- sample size. Factorswere %MFI, moon height, and will" units per minute of unbrokensong) might in- cloud (0-1 clear, 2-3 cloudy) for movement; %MFI, dicate an individual's level of arousal, I compared moon height, and wind (0-1 calm, 2-3 windy) for temposunder various light conditions. song;and %MFI and moon height for nest activity. Reproductiveactivity.--I monitored 5 successfulnests Differencesamong twilight, bright moonlight,and of 4 radio-taggedpairs from blinds about 6 m away. darknessscores were testedusing a Bonferroni Chi- During incubation, I recorded the number of times square(Miller 1966). Vocal and visitation responses the incubating bird left the eggs (nest departures), to taped song were analyzed for variance (ANOVA), either to feed or to allow a mate to assume incubation and between-categoryscores were testedby the Stu- duties.After hatching,I recordedthe number of times dent-Newman-Keuls procedure (SNK) (Sokal and adults fed the nestlings (nest feedings). Nests were Rohlf 1981).Song tempo measureswere subjectedto monitored for 14,690 min during incubation and for a Bonferroni t-test (Miller 1966), and a Chi-square 22,431 min during the nestling period. testwas usedto test the data for synchronybetween To assessthe possibility of a synchronized rela- the lunar month and the reproductivecycle. tionship between the lunar month and goatsucker reproductivecycles, I collected79 Caprimulgusnest records(from 38 different years)for which hatching RESULTS dateswere known or calculable.Whip-poor-will records camefrom Whedon (1906), Bailey (1912), Nau- Locomotoryactivity.--On moonless nights man (1925), Mousley (1937), Tyler (1940), Raynor Whip-poor-will activity appearedto end (dusk) (1941), Fowle and Fowle (1954), Kilham (1957), the and begin (dawn) when the sun was about 13ø Ontario Nest RecordsScheme (ONRS), the Marltimes Nest Records Scheme (MNRS), the North American below the horizon. A contingencytable for Nest RecordsProgram (NANRP), and this field study. moonless and moonlit (>25% MFI) conditions Other TemperateZone Caprimulgusdata came from verified this pattern for the periods when the Hewerr (1883), Gurney (1883), Soppitt (1883), Corbin sun was 10-13 ø and 13-16 ø below the horizon (1910), Lack (1930), and Berry and Bibby (1981) for (Fig. 1). Moonlight influenced activity only EuropeanNightjars (C. europaeus);from the SouthAf- when the sun was more than 13 ø below. At the 372 ALEXANDERM. MILLS [Auk,Vol. 103

39 39 were derived from those periods. Each of the 5 40- contextswas unique statistically,with moon- z light and twilight scoresbeing greater than 28 darknessscores (Fig. 3A). I witnessed60 salliesin 27 instancesof Whip- o poor-will feeding. Sallieswere short (g = 2.2 + 20, 0.1 m) and were usually upward rather than outward (g = 71 + 4ø). Nighthawks were recordedin 89 10-min periods. Seventy-five of these were during crepusculartwilight, and only 14 during the night. Twelve of the 14 occurred when the moon was 535 498 730 58 7 up, a significant departure from random (P = 0.014; binomial probability). Ten of the 12 moonlight sightings were made in periods of 10-13 ø 13-16 ø 76% or more MFI. Vocal activity.--Singing was a function of POSITION OF SUN BELOW HORIZON %MFI and moon height (Fig. 2B). The %MFI factor alone could predict amounts of night Fig. 1. The influence of moonlight on Whip-poor- singing. Wind was not a significant determi- will locomotory activity during the twilight-night nant, whereas %MFI and moon height were transition.Percentage movement is the percentageof highly significant(Table 1). telemetry readings taken (total readings are given below each column) that were moves. Open circles I comparedsinging levels among dusk,dawn, representmoonlight conditions (> 25%moon faceil- bright moonlight by %MFI, bright moonlight luminated) and closed circles represent moonless by height, and darkness,and found twilight conditions. There was no lunar influence when the levels comparableto thoseof bright moonlight sun was 10-13 ø below the horizon, but the influence (Fig. 3B). For dusk and dawn, I used peak pe- of the moon was significant for the 13-16ø position riods of the third through ninth 10-min pe- (X2 = 35.5, df = 1, P < 0.005). riods; this approximatescrepuscular twilight. Responsesto taped song for dusk, dawn, other extreme,activity began (dusk) and ceased moonlight (>50% MFI), and darkness are (dawn) when the sun was a few degreesbelow shown in Fig. 4. Only vocal responsesindicat- the horizon (Mills 1985). I will call the periods ed a nonrandom pattern (ANOVA Fs = 4.79, when the sun is between 4 ø and 13 ø below the df = 3,11, P < 0.05), even though males never horizon "crepusculartwilight." respondedby visitation in darkness(ANOVA Analysis of night telemetry data indicated Fs = 2.73, df = 3,11, 0.05 < P < 0.10). The over- that %MFI by itself was an adequate predictor all responsesuggests that darknessis unsuita- of activity levels (Fig. 2A). Moon height ap- ble for aggressiveencounters. pears to be a better predictor, but this is mis- An unmated male at the study site that sang leading due to the high correlation (r = 0.87) more than the mated birds had mean tempos between moon height and %MFI. The latter is of 51.8 songunits per min for twilight (n = 10), actually the better indicator becausemoons with 50.5 for bright moonlight (>75% MFI; n = 9), high %MFI are as likely to be low in the sky as and 39.2 for darkness (n = 5). Twilight and high, while all high moons have high %MFI. moonlight tempos were significantly greater The coefficients of determination (derived from than the darknesstempo (Bonferronit-test, P < partial correlation coefficients) indicated that 0.02). cloud cover, unlike %MFI and moon height, Reproductiveactivity.--Nest departures dur- was not a significant factor (Table 1). ing incubation (Fig. 2C) and nest feedingslater I comparedactivity levelsamong dusk,dawn, (Fig. 2D) indicated that activity levels in- bright moonlight by %MFI (>75%), bright creasedwith increasing%MFI and moon height. moonlight by height (>200 min above the ho- Percentageof MFI alone adequately predicted rizon), and darkness (no moon). Becausetwi- numbers of departures and numbers of feed- light activity occurred primarily during cre- ings. Coefficients of determination are shown pusculartwilight, duskand dawn activitylevels in Table 1. April1986] Moonlightand Goatsucker Behavior 373

4O' 37 A. MOVEMENT 28

PERCENTAGE 20

3880 311 490 914 3332 3880 2133 1847 1062

PERCENTAGE 20 MAXIMUM• 31 1['41 • 0 ' 3 ' • 807 59 108 230 515 t807 380 313 219

10 100{•EMRIN 10 5

3516 584 806 548 1778 3516 1901 1123 672

lO. lO

1000MIN o • ½ • 10 • 9 3558 125 431 874 8633 3556 2796 3433 1834

0 1-25 26-50 51-75 76-100 0 1-100 101-200 201-300

PERCENTAGE MOONFACE MOON HEIGHT ILLUMINATED (MINABOVE HORIZON) Fig. 2. The influenceof percentageof moon faceilluminated and moonheight on Whip-poor-will movement (A), song (B), nest departures(C), and nest feedings (D) during the night. Sample sizes are shown below each column.Because departures and feedingsare relatively rare events,numbers above columns in C and D are grossscores.

Nest departure and nest feeding activity, re- ly different for departures.There were signifi- spectively, for dusk, dawn, bright moonlight cantly higher levels at dusk than at dawn or in by %MFI, bright moonlight by height, and moonlight for nest feedings. In both cases, darknessare presentedin Fig. 3C and D. Twi- darknessscores were significantlythe smallest. light and moonlight levels were not statistical- I examined the relationship between lunar

TABLE1. Coefficientsof determinationfrom multiple partial correlationanalyses for amount of movement, amount of song, numbers of nest departures,and numbers of nest feedings during the night. % MFI = percentageof moon face illuminated.

Coefficient of Factor correlated determina- with score tion F, df P Movement % MFI 0.77 72.1 1,21 <0.005 Moon height 0.83 101.2 <0.005 Cloud 0.04 0.9 >0.25 Song % MFI 0.61 24.8 1,16 <0.005 Moon height 0.77 54.9 <0.005 Wind 0.01 0.1 >0.25 Nest departures % MFI 0.48 7.3 1,8 <0.05 Moon height 0.66 15.3 < 0.005 Nest feedings % MFI 0.44 6.4 1,8 <0.05 Moon height 0.77 27.5 <0.005 374 ALEXANDERM. MILLS [Auk,Vol. 103

60- PERCENTAGE'•I PERCENTAGE

40-

20' 1

0 2316 1902 1062 33• 3880 84 •5 449 219 807 DAWN• DUSK • A. MOVEMENT B. SONG

16' .15 NUMBER 36 NUMBER PER PER 1000 MIN 1000 MIN 11 10

8 18 14 12

672 3969 3509 1778 3516 6378 4434 1834 6633 3556 • DUSKDAWN • DUSKDAWN • • C. NEST DEPARTURES D. NEST FEEDINGS

Fig. 3. Comparisonsof Whip-poor-will activitiesduring dusk, dawn, bright moonlightby percentageof moon face illuminated (P), bright moonlight by height (H), and darkness(closed circles). Sample sizes are shown below each column. Breaksin lines above histogramsindicate statisticaldifferences (Bonferroni Chi- square test; P < 0.05). phaseand hatching date for Caprimulgus,Chor- only for orientation in caves (Griffin and deiles,and a random-numberdata set (Fig. 5). Thompson 1982, Fenton 1984). The use of Only Caprimulgusexhibited a synchrony be- acousticcues for finding food is well docu- tween the reproductiveand lunar cycles(X 2, mented in some nocturnal predators such as df = 9; Fig. 5). Hatching was centeredaround owls and bats (Payne 1971, Konishi 1973, Bell 10 daysbefore a full moon, a time when a wax- 1982),but a captive Common Poorwill (Phalae- ing moon is about 25% illuminated. noptilusnuttallii) feeding on flying moths did The young I observedusually made their first not respond until an insect came into the visual flights in their third week, and the youngestI field (Brauner 1953). My field observationsof saw make a feeding sally was 18 or 19 daysold. upward-directedsallies suggest that Whip-poor- Although the young fed themselvesby age 30 wills find food by exploiting backlit insecttar- days,they still acceptedfood from the parents. gets. Accordingto Harrison (1975), EuropeanNight- Goatsuckereyes have numerouselongated jars are independent at age 31-34 days. rods as well as tapeta lucida, which indicates extreme light sensitivity (Nicol et al. 1974). DISCUSSION Nonetheless, reduced foraging in darkness probably is due to visual constraintsrather than Lunarphiliain goatsuckers.--Myresult indi- to changesin insectavailability. catesthat conditionsmost suitable for foraging Most insects are lunarphobic (Williams and and territorial behavior occurduring twilight Singh 1951, Bowden and Church 1973), and and periods of bright moonlight. Moonlight only a few are lunarphilic (Kerfoot 1967, Jahn also enhancedgoatsucker song. 1982) or lunar-indifferent (Blair 1982, Snow Caprimulgids are not known to echolocate, 1982). Moths, apparently the favorite food of and birds that do apparently use echolocation Whip-poor-wills (Tyler 1940) and Common April1986] Moonlightand Goatsucker Behavior 375

• 1OO.

72 72 20 x VOCAL • 50. RESPONSE

I'- LU o 15 15 30 15 10'

VISITATION 42 (.3

CAPRIMULGUS CFIORDEILES RANDO• NUMBERS o 20• RESPONSE 15 15 30 15 74

10.4 3.5

DUSKDAWN •) P>0.3

Fig. 4. Vocal and visitation responses of male Fig. 5. Relationshipsbetween lunar phase and Whip-poor-will territory holders to intrusion (taped hatchingdate (N = number of clutches)for Capri- song).Percentage theoretical maximum is the strength rnulgus,Chordeiles, and a dataset generated from ran- of the responsebased on the scoring system. Open dom numbers. Lunar cycle is indicated by contrast- circle representsmoonlight conditions(>50% MFI) ing sine wave below each histogram. and closed circle representsdarkness. Numbers of test trials are shown below each column. Break in the line above vocal response columns indicates statisti- the parents, and as the cycle enters the next cal differences (SNK test). bright half, the improved foraging conditions allow the young to becomecompletely inde- Poorwills (Brauner 1952), are mostly lunarpho- pendent. bic (Morton et al. 1981, De Abreu 1982, Baner- The hatchingof clutchesat times other than jee and Mondal 1983,Stradling et al. 1983). Ev- thoseof maximal moonlight may be due to the idently, for improved foraging success, inexperience of young parents (Perrins 1970) increased light levels in moonlight more than or to failures of first clutches. After a nest fails, compensatefor reduction in insect numbers. the parents may not wait the better part of a The weak territorial responsesof Whip-poor- lunar cycle to begin again, especially at tem- wills in darkness may occur simply because perate latitudes where the breeding seasonis darknessis relatively unsuitable for territorial short.Chordeiles probably show no tendencyto encounters. It is also possible that temporary synchronizethe reproductive cycle with the torpor occurs during the dark periods of the lunar month becausethey are partially diurnal. night becausebirds exhibit short-term body Data for 7 pairsof double-broodedEuropean temperature fluctuations (Siegfried et al. 1975, Nightjars(Lack 1930)indicate a meanof 31.3 + McNab 1983) and becausegoatsuckers readily 0.4 days from first egg to first egg. The one enter torpor (Bartholomew et al. 1962, Ligon double-brooded Whip-poor-will pair in my 1970, Withers 1977). study began clutches33 days apart. These fig- For Caprimulgus,the first 2 weeks after egg ures are consistent with the possibility that hatching are the most sensitive for nestling consecutive broods are one lunar month (29.5 survival (Fig. 5), although the fifth and sixth days) apart so that both broods are in phase weeks one lunar month later, when the young with lunar cycling, although this could be for- gain independence, also may be important. I tuitous. American Goldfinches (Carduelistristis) suggestthat selectionhas favored parentsthat average 33.7 days (Stokes 1950) and Cedar synchronizethe first 2 weeks of the nestlings' Waxwings (Bombycillacedrorum) 29.8 days (Put- lives with the greatestamount of moonlight for nam 1949) between consecutive clutches. How- foraging. As the lunar month enters the fol- ever, the young of the first goatsuckerclutch lowing dark half, the developing indepen- are still dependent (the male assumedrespon- dence of the young alleviates the burden on sibility in Lack's casesand in mine) when the 376 ALEXANDERM. MILLS [Auk, VoL 103 second clutch is laid, indicating there is some ACKNOWLEDGMENTS urgency in starting the secondclutch. I gratefully acknowledgethe supervisionand ad- Chapin and Wing (1959) suggestedthat Sooty vice of Brock Fenton, and I am also indebted to Pat- Terns (Sternafuscata) on AscensionIsland used rick Weatherhead, Roland Thomas, Jaroslav Picman, the moon as a regulator and began a breeding and Richard Brewer for assistancein analysisand in cycle every 10 lunar months. Their data were preparationof the manuscript.Mark Kelly and fam- reinterpreted by Ashmole (1963), who rejected ily generouslyallowed me free use of their property, the lunar hypothesis.Other than in terns and and Catherine Weir and Rob Capell were dedicated goatsuckers,lunar influence on avian repro- and conscientious field assistants. I thank NSERC for ductivecycles is generallyignored (Murton and financial support throughout the study. Westwood 1977).

At the equator, crepuscular twilight lasts at LITERATURE CITED most for 39 min, while at my study site it lasts as long as 84 min. Therefore, the potential for ANTHONY, E. L. P., M. H. STACK,& T. H. KUNZ. 1981. exploitation of twilight by lunarphilic species Night roostingand the nocturnal time budget of decreasesnearer the equator, while that for the little brown bat: Myotis lucifugus:effects of moonlight (becauseof longer nights) increases. reproductive status, prey density, and environ- mental conditions. Oecologica (Berlin) 51: 151- Patterns of lunarphilia may be strongest in 156. equatorial regions. ASHMOLE,N. P. 1963. The biology of the Widea- Bats and nocturnal birds.--Worldwide there are wake or Sooty Tern Sternafuscata on Ascension almost700 speciesof animal-eating bats, most- Island. Ibis 103b: 297-364. ly insectivorous(Fenton 1982). Nocturnal ob- BAILEY,H.B. 1912. Notes on birds breeding in the ligate insectivorousbirds comprise 91 species mountainsof Virginia. Auk 29: 79-84. in 3 families (Clements 1981): potoos (Nycti- BANERJEE,T. C., & A. S. MONDAL. 1983. Factors af- biidae), owlet-nightjars (Aegothelidae), and fecting seasonalphenology of adult Scirophaga goatsuckers.Some of the approximately140 owl incertulas(Lepidoptera: Pyralidae). Indian J. Agr. Sci. 53: 77-82. speciesand probably someof the 13 frogmouth BARTHOLOMEW,G. A., J. W. HUDSON, & T. R. HOWELL. species(Podargidae) also eat flying insectsat 1962. Body temperature, oxygen consumption, night. Only about 15%of the world's vertebrate evaporativewater loss,and heart rate in the poor- nocturnal flying insectivore taxa are birds. will. Condor 64: 117-125. The general lunarphobia or lunar-indiffer- BELL,G.P. 1980. Habitat use and responseto patches enceexhibited by mostinsectivorous bats is not of prey by desertinsectivorous bats. Can. J. Zool. surprising, becausethe majority uses echolo- 58: 1876-1883. cation in at least part of the food detection pro- --. 1982. Behavioral and ecologicalaspects of cess (Fenton 1982). Echolocation, by circum- gleaning by a desert insectivorousbat, Antrozous venting the need for light, may seem superior pallidus(Chiroptera: Vespertilionidae). Behav. Ecol. Sociobiol. 10: 217-223. to vision as a method of prey detection. Fenton and Fleming (1976) suggestedthis holds only BERRY,R., & C. J. BIBBY.1981. A breeding study of nightjars.Brit. Birds 74: 161-169. for small insectivores, however, and costs of BJORKLUND,R. G., & E. R. BJORKLUND.1983. Abun- echolocation such as warning sonar-sensitive dance of Whip-poor-wills, Caprimulgusvociferus, potential prey (Miller and Oleson 1979,Fenton in the Sand Ridge State Forest. Trans. Illinois and Fullard 1979) and atmospheric attenuation State Acad. Sci. 76: 271-276. (Griffin 1971) may favor vision in some cases. BLAIR,B. W. 1982. Seasonalabundance of Agrotis Evidence for interactions between birds and segetumand Agrotisipsilon (Lepidoptera: Noctui- bats is scarce.Shields and Bildstein (1979) found dae) in Zimbabwe and a method of forecasting that vespertilionid bats appeared to dominate post-winterpopulation densities. J. Entomol.Soc. South Africa 45: 201-216. Common Nighthawks in aggressiveencounters at a food sourcelocalized at a light. Most BOWDEN,J. 1973. The influence of moonlight on catchesof insectsin light-traps in Africa. Part I. flying insectsprobably are not defensible as The moon and moonlight. Bull. Entomol. Res. food, however (Brown 1964). This, and the sub- 63: 113-128. division of the nocturnal flying insectivore --, & B. M. CHURCH. 1973. The influence of niche through differences in size, foraging moonlight on catchesof insectsin light-traps in strategies,and sensorymodalities, may reduce Africa. Part II. The effectof moon phaseon light- the potential for bird-bat competition. trap catches.Bull. Entomol. Res.63: 129-142. April1986] Moonlightand Goatsucker Behavior 377

BRAUNER,J. 1952. Reactions of poor-wills to light KONISHI, M. 1973. How the owl tracks its prey. and temperature.Condor 54: 152-159. Amer. Sci. 61: 414-424. 1953. Observations on the behavior of a LACK,D. 1930. Double-broodingof the nightjar.Brit. captivepoor-will. Condor 55: 152-159. Birds 23: 242-244. BROWN,J. L. 1964. The evolution of diversity in LIGON,J.D. 1970. Still more responsesof the poor- avian territoriality. Wilson Bull. 76: 160-169. will to low temperatures.Condor 72: 496-498. CHAPIN,J.P., &. L. W. WING. 1959. The wideawake McNA•, B. K. 1983. Energetics,body size, and the calendar, 1953 to 1958. Auk 76: 153-158. limits to endothermy. J. Zool. 199: 1-29. CLEMENTS,J. 1981. Birds of the world: a checklist. MILLER,L. A., & J. OLESON. 1979. Avoidance behav- London, Croom Helm. ior in greenlacewings. I. Behaviorof free flying COOPER,R. J. 1980. Relative abundance of Georgia lacewings to hunting bats and ultrasound. J. caprimulgidsbased on call counts.Wilson Bull. Comp. Physiol. 131: 113-120. 93: 363-371. MILLER,R. G., JR. 1966. Simultaneous statistical in- CORBIN,G.B. 1910. Late eggs of nightjar (Caprimul- ference. New York, McGraw-Hill. guseuropaeus): was it a secondbrood? Zoologist MILLS, A.M. 1985. The influence of moonlight on 14: 339-340. the behaviour of goatsuckers(Caprimulgidae). Unpublished M.Sc. thesis,Ottawa, Carleton Univ. DE A•REU,J.M. 1982. Investigationson the rubber leaf caterpillarErrinnyis ello in Bahia,Brazil. Rev. MORRISON,D.W. 1978. Lunar phobia in a neotrop- Theobroma 12: 85-100. ical fruit bat, Artibeusjamaicensis (Chiroptera: FENTON,M.B. 1974. The role of echolocation in the Phyllostomidae).Anim. Behav.26.' 852-855. MORTON, R., L. D. TUART,& K. G. WARDAUGH. 1981. evolution of bats. Amer. Natur. 108: 386-388. The analysis and standardization of light-trap 1982. Echolocation, insect hearing, and catchesof Heliothisarmiger (Hubner) and H. punc- feeding ecology of insectivorousbats. Pp. 261- tigerWallengren (Lepidoptera:Noctuidae). Bull. 285 in Ecology of bats (T. H. Kunz, Ed.). New Entomol. Res. 71: 207-225. York, Plenum Press. MOUSLEY,H. 1937. A study of the home life of the 1984. Echolocation:implications for ecolo- eastern Whip-poor-will (Antrostomusvociferus). gy and evolution of bats. Quart. Rev. Biol. 59: Can. Field-Natur. 51: 73-77. 33-53. MURTON,R. K., & J. WESTWOOD.1977. Avian breed- --, & T. H. FLEMING. 1976. Ecological interactions between bats and nocturnal birds. Biotro- ing cycles.Oxford, Clarendon Press. NAUMAN,E.D. 1925. The Whip-poor-will: its pros- pica 8: 104-110. -, & J. H. FULLARD.1979. The influence of moth pectsof survival in southernIowa. Wilson Bull. 37: 203-206. hearing on bat echolocationstrategies. J. Comp. NICOL,J. A. C., F. R. S. ARNOTT,& H. J. ARNOTZ. 1974. Physiol. 132: 77-86. Tapetalucida in the eyes of goatsuckers(Capri- FOWLE,C. D., & A.M. FOWLE. 1954. Observations at mulgidae). Proc. Royal Soc. London, Ser. B 187: a Whip-poor-will'snest. Can. Field-Natur. 68: 37- 349-352. 39. PAYNE,R.S. 1971. Acousticlocation of prey by Barn GRIFFIN,D.g. 1971. The importance of atmospheric Owls (Tyto alba).J. Exp. Biol. 54: 535-573. attenuationfor the echolocationof bats (Chirop- PERRINS,C.M. 1970. The timing of birds' breeding tera). Anim. Behav. 19: 55-61. seasons. Ibis 112: 242-255. --, & D. THOMPSON.1982. Echolocationby cave PUTNAM,L.S. 1949. The life history of the Cedar swiftlets. Behav. Ecol. Sociobiol. 10: 119-123. Waxwing. Wilson Bull. 61: 141-182. GURNE¾,J. H., JR. 1883. Late nesting of the nightjar. RAYNOR,G.S. 1941. The nesting habits of the Whip- Zoologist 7: 429-430. poor-will. Bird-Banding 12: 98-104. HARRISON,C. 1975. A field guide to the nests,eggs, SHIELDS,W. M., & K. L. BILDSTEIN. 1979. Birds versus and nestlings of British and European birds. bats: behavioral interactions at a localized food London, Collins. source.Ecology 60: 468-474. HEWETT,W. 1883. Late nesting of the nightjar. Zo- SIEGFRIED,W. R., R. L. ABRAHAM, & V. B. KUECHLE. ologist7: 380-381. 1975. Daily temperaturecycles in Barred,Great JAHN,E. 1982. Studies on the attack on spruce trees Horned and Snowy owls. Condor 77: 502-506. by bark beetlesin connectionwith moon phase. SIMMONS,J. A., & R. A. STEIN. 1980. Acoustic im- Anz. Schaedlingskd. Pflanz. Umweltschutz. 55: aging in bat sonar:echolocation signals and the 145-149. evolution of echolocation.J. Comp. Physiol. 135: KERFOOT,W.B. 1967. The lunar periodicity of Sphe- 61-84. codogastratexana, a nocturnal bee (Hymenoptera: SNOW, W.F. 1982. Further observations on the ver- Halictidae). Anim. Behav. 15: 479-486. tical distributionof flying mosquitoes(Diptera: KILHAM, L. 1957. Egg-carrying by the Whip-poor- Culicidae) in West African savanna. Bull. Ento- will. Wilson Bull. 69: 113. mol. Res. 72: 695-708. 378 ALEXANDERM. MILLS [Auk,Vol. 103

SOKAL,R. R., & F. J. ROHLF. 1981. Biometry. San VOHDEN, R. A., & F. G. SMITH. 1983. The astronom- Francisco, W. H. Freeman. ical almanacfor the year 1984.Washington, D.C., SOPPITT,H. T. 1883. Late nesting of the nightjar. U.S. Government Printing Office and London, Zoologist 7: 429. Her Majesty'sStationery Office. SPRUNT,A., JR. 1940. Chuck-will's-widow. Pp. 147- WHEDON,A.D. 1906. With the Whip-poor-wills. 162 in Life histories of North American cuckoos, Bird-Lore 8: 83-87. goatsuckers,hummingbirds, and their allies (A. WILLIAMS, C. B., & B. P. SINGH. 1951. Effect of moon- C. Bent, Ed.). U.S. Natl. Mus. Bull. 176. light on insectactivity. Nature (London) 167:853. STOKES,A.W. 1950. Breedingbehavior of the Gold- WITHERS,P. C. 1977. Respiration,metabolism, and finch. Wilson Bull. 62: 107-127. heat exchangeof euthermic and torpid poorwills STRADLING,D. J., C. J. LEGG,& F. D. BENNET]'. 1983. and hummingbirds. Physiol. Zool. 50: 43-52. Observationsof the Sphingidae(Lepidoptera) of WYNNE-EDWARDS,V. C. 1930. On the waking-time Trinidad. Bull. Entomol. Res. 73: 201-232. of the nightjar (Caprimulguse. europaeus).J. Exp. TYLER,W.M. 1940. EasternWhippoorwill. Pp. 163- Zool. 7: 241-247. 183 in Life histories of North American cuckoos, goatsuckers,hummingbirds, and their allies (A. C. Bent, Ed.). U.S. Natl. Mus. Bull. 176.