Breeding Biology of the Puerto Rican Sharp-Shinned Hawk (Accipiter Striatus Venator)

BREEDING BIOLOGY OF THE PUERTO RICAN SHARP-SHINNED HAWK (ACCIPITER STRIATUS VENATOR)

CARLOS A. DELANNOY • AND ALEXANDER CRUZ 2 •Departmentof Biology,University of PuertoRico, Mayaguez, Puerto Rico 00708, and 2Environmental,Population, and Organismic Biology Department, University of Colorado, Boulder,Colorado 80309-0334 USA

AI3STRACT.--Westudied the breedingbiology of the Sharp-shinnedHawk (Accipiterstriatus venator)in Maricao forest of western Puerto Rico from 1978 to 1985.Sharp-shinned Hawks are year-roundresidents and establishnesting territoriesonly during the breeding season, which coincideswith the dry and beginningof the wet seasons.Nesting siteswere occupied in Decemberand Januaryevery year and reoccupancyrates were 50% or higher. Prolonged and intense territorial conflicts between mated and unmated males were common. The onset of egg-layingwas in late March or earlyApril approximately3-4 monthsafter occupancyof nesting sites. Laying of first clutchespeaked in early April and spanned 38 days (n = 19 clutches).Laying of secondclutches occurred irregularly and spanned 55 days(n = 8 clutches). Femalesrenested only after the initial clutchor broodwas lost.The incubationperiod was 32 days (n = 13 clutches), similar to the duration reported in temperate North America. Nestling femalesattained larger asymptoticmass than males,but the latter grew faster; althoughthe slopesof the regressionlines were statisticallyhomogeneous. Males fledged at an averageage of 28.2 daysand femalesat 32.1 days.Young were slightly heavierthan adults at fledging,but the wing chord and tail lengthswere approximately50% shorter than those of adults. Fledging occurredat the peak of prey abundance.The breeding cycle in Puerto Ricowas approximately 2 monthslonger than that recordedin Oregonand Utah. The time that elapsedfrom occupancyof nestingsites to egg laying accountedfor the differences. Juvenilesdeparted from nestingsites when prey was still abundantbut delivery rateshad declined considerably.A total of 105 eggswas laid in 40 nests(average clutch size 2.6), of which 63%hatched and 47%of the nestlingsfledged. A total of 0.8 youngfledged per breeding attempt.Overall nest successwas 29%,36% (n = 33 nests)in first nestingattempts and 0% in secondnesting attempts (n = 9 nests).Most reproductivelosses in 28 nestsresulted from nestlingmortality from Philornissp. (Diptera, Muscidae)(n = 9) and desertionof clutches(n = 11). Fecundity and reproductive successwas lower in Puerto Rico than in Oregon, Utah, and Wyoming.Despite low reproductivesuccess in Maricaoforest, the breedingpopulation did not decline during our study.Received 29 June1987, accepted 9 May 1988.

RELATIVELYlittle is known aboutthe breeding temperate counterparts(Liversidge 1962; Ben- biology of raptorsin tropical regions,particu- son et al. 1971; Smeenk 1974; Smeenk and larly in the Neotropics.Due to the lack of de- Smeenk-Enserink 1975, 1977; Thiollay 1975; tailed information on tropical species,only lim- Brown 1976; Snyder and Wiley 1976; Faaborg ited comparisons within and between et al. 1980; ffrench 1980; Mader 1981, 1982; Wi- geographicregions are possible.We selected ley and Wiley 1981).Breeding cycles are longer the Sharp-shinnedHawk (Accipiterstriatus) as a in tropical birds of prey, in part becauselaying model speciesto examine reproductive adap- occursat almost any time of the year (Mader tationsin a tropical environment (Puerto Rico), 1982). Furthermore, tropical species have relate breeding adaptationsto its ecology,and breedingseasons that are restrictedto either the comparebreeding featureswith those of con- wet or dry season(Benson et al. 1971; Mader specificsin temperateNorth America(e.g. Bent 1981, 1982). The duration of someof the stages 1937;Craighead and Craighead1956; Platt 1973; of the breeding cycle (such as incubation and Snyder and Wiley 1976;Hennessy 1978;Reyn- nestling periods) are generally longer in the olds 1978, 1983; Reynolds and Wight 1978; Tropics(Newton 1979, Mader 1982). Although Reynoldsand Meslow 1984;Mueller et al. 1981). reproductive rates and nest successare com- Tropical birds of prey have longer breeding paratively lower in tropical areas,survival of seasonsand lower reproductiverates than their fledglingsand adults is as high as in temperate 649 The Auk 105: 649-662. October 1988 650 DEt•,NNOYAND CRUZ [Auk,Vol. 105 areas(Mader 1982). Also, sometropical raptors length was taken from the baseto the tip of the center lay replacement clutchesafter losing eggs or rectrix. young, which rarely occursin temperateareas Productivity was production of fledglings related (Newton 1979, Mader 1982). to size of nesting population (including territorial nonbreeders). Reproductive output was the total number of fledglingsproduced over a period of time. Reproductivesuccess was a general term that includ- STUDY AREA AND METHODS ed several measuresand components,expressed on a Our study was in Maricao forest (4,150 ha), at the per pair, per breeding attempt, or per egg basis. To determine bird-prey abundance in the Maricao west end o[ the Cordillera Central (18ø09'N, 66ø58'W). forest, 3 transects(4 km total) were established (Cruz Elevationsranged [rom 550 m in the subtropicalmoist and Delannoy 1984). Bird densities were estimated [orest to 900 m in the subtropicallower montanewet by the variable strip method (Emlen 1971). Parallel [orestlife zones.Precipitation ranged [rom 57 mm in lines on both sidesof the transectroutes, 5 m apart January to 374 mm during October (annual mean to a distanceof 30 m, defined the stripsof coverage. 2345.4mm, 1971-1982).Mean monthly temperatures Lateral distanceof bird speciesfrom the transectroute ranged from 20.1øCin Januaryto 23.2øCin August (annual mean 21.8øC; National Oceanic and Atmo- was estimatedby visual or aural detection.To reduce bird-count variability introduced by observers'bias, sphericAdministration 1972-1982).The li[e zonesand only Delannoy conductedthe censuses.The transect vegetationare described by Ewel and Whitmore(1973), and Cruz and Delannoy (1984). count for a specieswas transformedinto a density estimateby dividing the number of individuals per The breeding grounds were visited regularly area coveredby the coefficientof detectabililty (Em- throughout the breeding seasonto find mated pairs. len 1971, 1977). Each transect route was censusedtwice We defined nesting site as an area where aerial dis- a month on consecutivedays from June to August plays, mating and nest-building, adult incubating, 1980 (18 counts),from Januaryto August 1981 (48 brooding, and repeated prey-carrying occurred.An counts),and from May to August 1982 (24 counts). area with a mated pair was consideredan occupied Censuses were initiated 30 min after sunrise and com- nesting site. Observations of Sharp-shinned Hawks pleted within 1-2 h. Counts proceededonly when on their breeding grounds were made from above- there was 30% overcast or less, little or no wind, and canopy lookoutsand ground blinds with the aid of nonfoggy conditions. binocularsand a spottingscope. To reducedifficulty A total of 333 h was spent at 4 neststo observe the in determining whether an observationpertained to movementsand behavior of fledglings and determine courtshipor territorial behavior, display flight was the rate of prey delivery by adults.These observations categorizedas territorial only if followed by encounters between the resident and intruders. were initiated midway through the nestling period and continued until young departed. All statistical The incubation period was the time (days) [rom proceduresfollowed Sokal and Rohlf (1981). laying to hatching (after clutch completion) o[ the last egg. We measured egg dimensions (length and width) to the nearest 0.1 mm with vernier calipers, RESULTS and determined egg massand body massof nestlings to the nearest0.1 g with a Pesolaspring scale.Indi- Reoccupancyof nestingsites.--Puerto Rican vidual young were markedwith an inert organicdye Sharp-shinnedHawks are year-round residents ([ood coloring) on the crown soonafter hatching.Sex o[ nestlings was inferred [rom differencesin body that establishnesting territories only during massand size developed during growth. Growth pat- the breeding season.Nesting sites are reoccu- terns o[ male and [emale nestlings were described pied in December and January. Nesting sites graphically. Rickle[s' (1967) method o[ fitting equa- had relativelyhigh reoccupancyrates (Table 1). tions to growth curveswas usedto comparemale and Nine sites were used at least twice. Five had female growth patterns. Growth curves were fitted reoccupancyrates of 80%or higher, while none mostclosely by the logisticequation and logisticcon- of the remaining 4 nesting sites had reoccu~ stants were used for comparisons.Shortly before pancy rates of less than 50%. A banded adult fledging,young were bandedwith USFWSaluminum femalereoccupied the samenesting site in 1981, bands and colored leg bands. Mist nets were used to 1982, and 1983. Another banded female re- capturefledglings and adults,which were measured turned to the same nesting site in 1982, 1983, (length o[ tarsus, wing chord, culmen, and tail), weighed, and checkedfor ectoparasites.Tarsal length and 1985.Newton (1986) reportedaverage pe- was measuredfrom the intertarsaljoint to the bend riods of residenceon nesting sites of 1.4 yr in of the foot. Wing chord was the distance from the male and 1.5 yr in female Eurasian Sparrow- bend to the tip o[ the longestprimary. Culmen length hawks(Accipiter nisus). Two maleshad residence was measured from the cere to the bill tip. The tail periods of 4 and 5 yr, and 5 females had been October1988] Sharp-shinnedHawk Breeding Biology 651 present 5-6 yr. A third female banded in 1981 TABLE1. Reoccupancyrate of Sharp-shinnedHawk moved 1.7 km to a different nestingsite in 1982. nesting sites in western Puerto Rico.

A female banded as a nestling in 1979 used a Years nestingsite 1.1 km away from her natal areain occupied/ 1983. Eurasian Sparrowhawk females moved a years Reoccupancy median distance of 1.5 km and males 0.8 km, Nesting site checked rate and maximum distances of 27 km and 19 km, Rio Grande 2/4 0.50 respectively (Newton 1986). Of the 42 nests Rio Bonelli 4/4 1.00 studiedfrom 1978to 1985,only 4 were occupied Merenderos 7/7 1.00 Quinina 4/5 0.80 by immature-plumagedfemales, and none by Casa de Piedra 5/6 0.83 immature males. Cain Alto 4/6 0.67 Courtship and territoriality.--Most Sharp- Buena Vista 4/7 0.57 shinned Hawk activities during Decemberand Camping area 3 / 6 0.50 Januaryconsisted of courtshipand territorial Descanso 5/6 0.83 displayflights. Males and femalesinitiated display flights shortly after sunriseand, in some sites,continued until mid-morning. A typical iors. In one instance the resident male flew in courtshipflight began when the male circled circles above the intruder and dove twice until above the nesting site; the female followed the intruder left. On three occasions conflicts shortly afterwards.Adults mixed soaring and reachedhigh intensity,and malesgrappled tal- rapid flights, calling intermittently. The male ons and spun laterally to a few metersfrom the used flapping flight more frequently, and cir- canopybefore breaking loose (n = 1), or landed cled higher, than the female. Birds reachedes- on the ground with locked talons, thrashed timatedabove-canopy heights of 20 to 200 m (œ wings at each other, and finally broke loose(n = 140 m, n = 44). At irregular intervals male = 2). In all three instancesafter separating,the and female independentlyperformed an un- resident chased and evicted the intruder from dulating flight display that consistedof a re- the nesting site. Conflict between males per- peated series of shallow and deep dives fol- sistedfor severalmonths (February-May) in 2 lowed by a recovery of height. The hawks nesting sites. We recorded 20 encounters be- frequently held a stationaryposition in midair tween intruder and resident male, but only 2 and plungedvertically, or nearlyso, with closed (10%) ended in physical contactand thrashing wings accompaniedby repeated quickening wings in midair. Intruders were evicted in all movementsof the wings. On deep dives, they 20 encounters. The rate of intrusion was 0.59/h dropped for several secondsand recovered a of observations (20/34). The intruder male car- short distancefrom the canopy.We did not ob- ried prey into the nestingsite twice. The female servethe performerdirect the latter displayto- acceptedprey once in the absenceof the resi- wards the other member of the pair. Display dent male. At no time did the intruder male bouts lasted from 3-20 min (• = 13 min; n = attempt to copulate with the female. The in- 44), and were repeatedseveral times. All court- truder also carried nest material and deposited ship flights (n = 44) ended with a deep dive it on the nest while the female was incubating into the forest.Courtship flights normally were (n = 4). followed by courtship-feeding,matings, and Nest building.--Most Sharp-shinned Hawks nest building. started nest constructionshortly after perma- We observed19 territorial displayflights be- nently occupyingtheir sitesin January.How- tween nonspecificmales in 5 nesting sites in ever, the hawks added little nesting material 1981. Resident males initiated territorial behav- (sticksand twigs) at this stageand construction ior from a perch (n = 3) or from the air (n = proceededslowly. Bothsexes became more ac- 16).When intruder malesentered air spacenear tive in the nest-buildingprocess 3-4 weeksbe- the nestingsites, resident males flew straightat fore laying eggs. them,chasing them. Both males normally called We observedthe nest-buildingprocess in 1 repeatedly.The residentmales usually evicted pair. On 10 February 1981 the pair had laid the the intruders (n = 15). Some intruders did not foundationof the nestplatform (approximately leavethe nestingsites immediately, and the res- 1-2% of the completednest's size). During 4.5 ident males respondedwith 2 different behav- h of observationon 20 Februarythe malemade 652 DEi.•i•i,ao¾ Ai•ii• CRVZ [Auk, Vol. 105

11 trips to the nest with nest material; the fe- North America were 37.5 mm x 30.4 mm (n = male made none. On 5 March, the male made 58, Bent 1937). The average egg masswas 18.5 62% of trips and the female, 38% (n = 42) in g, 10.8%of the female's body massand 32% of 1 h. On 15 March, the male made 11% of trips her massfor a clutch of 3 eggs.Sharp-shinned while the female made 89% in 1 h (n = 36). In Hawk eggs in temperate North America aver- all, males made 46% of the trips and females aged 19 g, 11% of the female's body massand 54% (n = 89). 53% for the usual 5-egg clutch (Newton 1979). Nestswere built on trees;branches and twigs Only femalesincubated while males provid- were gatheredfrom the groundand nearbytrees, ed food. Similar behavior has been reported for and the nest bowl was lined with a layer of populationsin temperateNorth America (Sny- finer twigs. No additional nest material was der and Wiley 1976). In 1981, we recorded the added. Although most pairs built a new nest incubation pattern of a female during 12-h pe- every year, some did not. In 2 nesting sites in riods (0600-1800) for 3 consecutivedays. The 1983, for example,the banded pairs reused the female incubatedthe first egg 27% of the ob- samenests they built in 1982.Also, somepairs servationperiod the first day, a clutch of 2 eggs built alternatenests and usedthem after failing 32% of the observationperiod the secondday, in their first nesting attempt. We observedthis and 42% the third day with still 2 eggs. Al- behaviorat 2 sitesin 1982.Near nestcompletion though the incubationperiod varied among fe- the pair gave shape to the nest bowl by tram- males,it is possiblethat full incubation begins pling the layer of finer twigs with their talons with the third egg. The incubation period from and breast. laying to hatching of the last egg was 32 days Egg laying,incubation, and hatching.--ByFeb- (n = 13 nests). In temperate North America, ruaryfemales stopped hunting and stayed near Sharp-shinned Hawks have incubation periods the nest. Three femalessettled permanently on of 30-32 days(Platt 1973,Hennessy 1978, Reyn- their nesting sites on 14, 15, and 25 February olds and Wight 1978). 1981. They spent most of their time resting on We determined the hatching sequence of 9 branches("pre-laying lethargy," Newton 1979). eggs in 3 nests.The first and secondeggs laid Males provided all the food at this stage and (n = 6 eggs) hatched lessthan 24 h apart. Third during the following months. eggs (n = 2 clutches)hatched between 36 and Eggs were laid during the dry seasonfrom 48 h after the second-laideggs. In the remaining March to July (n = 27 clutches)(Fig. 1). Laying clutch,the third egg laid hatchedapproximately of first clutches spanned 38 days (16 March to 24 h after the second. Fifteen first clutches 22 April, n = 19 clutches).Earliest recorded lay- hatched over a period of 38 daysfrom 20 April ing dateswere 9 April 1978, 21 March 1979, 24 to 27 May (Fig. 1).Three second clutches hatched March 1980, 18 March 1981, 15 March 1982. The in the late dry and early wet seasonon 4 June, number of first clutchespeaked in early April. 16 June, and 5 July. Femalesrenested only after losingthe firstclutch Nestling period.--Young emerged from the or brood. Secondclutches occurred irregularly eggswith their eyesopened. A few hourslater from 12 May to 5 July, a span of 55 days (n = the white natal down dried. They uttered "peep" 8). Secondclutches peaked in late May and early calls in responseto the approachof the female June. It took 2 females approximately 27 and 30 or any object,such as a reachinghand. The young days,respectively, to lay again after losing their raised their headsand acceptedtiny morselsof first broods.Females laid mosteggs on alternate prey presented by the female. By the second days until clutch completion. We determined and third day after hatching (day 0 at hatching) egg-layingsequences in 3 clutches(n = 8). Sev- the young showed improved coordination in en of 8 eggswere laid on alternatedays, while pecking at the food held above them by the 1 egg was laid the following day. The most female. At 4 days of age, the young performed common clutch was 3, and the average size of poorly coordinatedpreening movementsof the first clutchesdid not differ significantly from breast. second clutches (Table 2). About a week after hatching, differences in Mean dimensions of Puerto Rican Sharp- plumage developmentbetween the male and shinned Hawk eggs were 37.6 mmx 29.5 mm female nestlings were apparent. The primary (n = 49, Table 3). Similarly, averagedimensions feather tips of malesemerged from the sheaths of Sharp-shinned Hawks eggs in temperate at approximately 6-7 days and, in females, 8 October1988] Sharp-shinnedHawk Breeding Biology 653

TABLE2. Averageclutch size of Sharp-shinnedHawk Egg laying first and second clutches. lO N=27 No. No. No. Average 5 1-egg 2-egg 3-egg clutch nests nests nests size a

First clutches 4 2 25 2.68" J F M A M J J A S 0 N D Second clutches I 3 5 2.44 a Total 5 5 30 2.63 • 10 N•18 ' Mann Whitney test U = 172, P > 0.05.

did not observe males dismembering prey, E 5 I • feeding young, or brooding. Femalesbrooded Z• tI•l•111 II•l•l•111111111Hatching and fed prey to the young. Everytimethe adult JFMAMJ JASOND malesarrived with prey, they gave a "contact call" from a nearby perch, stimulating the female to leave the nestto obtain the prey. Shortly 1 N=8 after malessurrendered the prey to the females, they typically flew to the nest, stared at the young momentarily, and then departed. Fe- malesnormally returned to the nest, tore apart •1,I 'l'l •1 •lglFledging •1 II ,III II II JFMAMJ J ASOND the prey and fed the young. 600 During the third week after hatching (16-23 days) females spent less time brooding. They 5OO perched near the nest and waited. When prey E 400 was delivered, they dismemberedit for the E young. In one nest the female brooded three ._= 300 16-day-oldyoung 57%of the time (n = 9.25 h), but decreasedbrooding to 5% (n = 4 h) when c:: the young were 23 days old. They were last brooded at 26 days and brooding was limited to a period of rainy weather. J•F•M'A'M•J •J•A"S10•N•D • During the fourth week after hatching (24- 31 days),the young squabbledover prey deliv- Fig. 1. Breedingcycle of the Puerto Rican Sharp- shinned Hawk in Maricao forest relative to rainfall eredby malesand were ableto dismembermost pattern. Vertical lines in rainfall graph represent1 of its soft parts. Upon her return to the nest the SD above and below mean values. There were no adult female assistedthe young in dismember- fledgingsfrom secondclutches. ing the harder portions of the prey. At 25-27 days the young flapped their wings regularly and jumped acrossthe nest or into nearby days. The first tail feathers appeared at approx- branches and began to roost overnight in imately 9-10 days in males, and 11 days in fe- branches. males.In the secondweek after hatching,a white The nestling period ended when the young down, "wooly" in appearance,began to replace flew short distances from the nest and roosted the natal down. Young flapped the,ir wings for in trees 10-15 m distant. Eleven males fledged the first time at 12 days and emitted "alarm at an averageage of 28.2 days(SD = 1.17,range calls" when we climbed the nest tree or reached into the nest. At age 13-15 days they showed TABLE3. Dimensions and mass of Sharp-shinned defense displays to our reaching hand. They Hawk eggs. uttered "alarm calls," sat on their tarsometatarsi and, with spreadwings, presentedtheir claws. Feature n Mean SD Range During the nestlingperiod, males hunted and Length (mm) 49 37.6 0.93 36.4-39.8 delivered avian prey to the females,or dropped Width (mm) 49 29.5 0.57 28.1-31.2 Mass (g) 8 18.5 0.41 18.0-19.0 it in the nests and departed immediately. We 654 DEL•NNOYAND CRUZ [Auk,Vol. 105

TABLE4. Comparisonof growth-rate parametersof male and female Sharp-shinnedHawk nestlings.

Males Females Y=-0.61 +.069X ß/7 Component (n = 13) (n = 11) Nestling period (days) 28.2 32.1

Adult mass(g) = W 94.9 170.9 060X Asymptote (g) = A 102.0 172.0 R = A/W 1.07 1.01 K 0.28 0.24 to(inflection point) 8.8 II.0 t10-t•o 16.2 18.3 KR/4 x 100 (%/day) 7.4 6.1 KA/4 (g/day) 7.0 10.3

ß MALES,

= 27-30), and 9 femalesat 32.1 days(SD = 1.05, range= 30-33), with a combinedaverage fledg- • 0FEMALES. N=11 ing age of 30.0 days (SD = 2.28, range = 27- 33). ' ' '"' 16' ' 20' ' 22.... 24 2•0 Growth rate.--Male and female nestlings ^•E (D^¾$) showed differencesin growth patterns (Table Fig. 2. Growth of nestlingSharp-shinned Hawks. 4). Femalesattained a higher asymptoticmass Circlesrepresent mean values.Slopes are statistically than malesbut the latter grew faster,although homogeneous.F = 0.003, P > 0.05. the slopesof the regressionlines were statistically homogeneous(Fig. 2). K, a constantcal- culated from the slope of the regressionline occurred in or near the nest. Adults delivered that representsthe rateat which asymptoticmass prey to the nest. was reached,was higher in malesthan females. By 40-47 daysafter hatching,the youngbe- The maximumgrowth rate in g / day (KA / 4) was camestrong fliers, chasedeach other, and dis- greater for females than males, but when ex- persedto 50-75 m from the nest.Adult females pressedas a percentageof adult mass(KR/4 x still fed young at this time. Adults were com- 100), males attained adult mass 1.05 times faster monly interceptedimmediately after being de- than females.It tookmales 8.8 daysto grow half tected by young, and adults surrenderedprey their asymptoticmass (to) but 11 days for fe- in midair to the firstyoung to arrive.The young males. The time interval of growth from 10- were capableof handling and carrying prey to 90% of the asymptote(t•0-t9o) was shorter in a perch away from their siblings,where it was males than females. Males fledged before fe- consumed. males. The young at fledging were slightly Two young maleseach attemptedto capture heavier than adults. prey for the firsttime at an ageof 47 days.One Growth of body parts in young near-fledging flew after a Grey Kingbird (Tyrannusdominicen- to the ageof recapturewas compared to average sis), the other, at an Emerald Hummingbird adult body size (Table 5). All young lost mass (Chlorostilbonmaugaeus). Both attemptswere un- from near fledging to the recaptureage. The successful.We observed12 other attemptswith- tarsi of all young also grew slightly between in 100 m of the neststo captureprey by young the intervals compared.The most notable dif- whose ages ranged between 51 and 68 days. ference in growth between these ageswas in Youngmales were involved in 9 of theattempts, the length of the wing chord and tail, growth femalesin 3. Young attemptedto capturebut- incrementsof 23, 35, 37, and 48%in wing-chord terflies(5 attempts),Emerald Hummingbirds (3), length,and of 40, 47, 50, and 53%in tail length. Zenaida Doves (Zenaidaaurita; 2), and Anolisliz- Fledglingperiod and dispersal.--Observations ards(2). They succeededin catchingonly Anolis of adultsand young were continued at 4 nesting lizards. Although we tried to monitor move- sitesuntil young departed.Between 32 and 39 ments of all young within the nest areas, at days from hatching, most activities of young times we lost visual contactand other attempts October1988] Sharp-shinnedHawk Breeding Biology 655

T^BLE5. Growth of Sharp-shinnedHawk young betweentwo ageperiods relative to adult values,a reported as percentage.

Age period % adult wing % adult % adult (days) Sex % adult mass chord length tail length tarsuslength 26- 50 fe male 99-91 61-98 55-95 97 - 102 26-50 female 99-94 53-101 42-95 94-99 26-50 male 110-103 68-103 48-98 104-107 26-43 female 104-97 69-92 48-95 91-93

' Averagemass (g) and averagebody measurements(mm) of adults:male--mass = 94.9, wing chord = 141.0,tail length • 116.3,tarsus length = 45.7; female--mass= 170.9,wing chord = 174.4,tail length = 139.9,tarsus length = 56.4. at predation were presumable unobserved. shorter period becauseno secondnests were Twice when we lost visual contactof 2 young successful.Egg-laying and hatching occurred malesfor 45 rain, their cropswere full when mostlyduring periodsof low prey abundance spotted. (Fig. 4). Young fledgedduring the peak of prey Young spenttime away from the nestarea 1- abundance.No bird prey density data were 2 daysbefore departingfrom the nestingsite. availablefor the lastquarter of the year. Despite In 1982 we monitored movementsof 6 young theselimitations, it appearsthat Sharp-shinned at 2 nesting sites.Two young, 1 in each of the Hawks have nestlingsand fledglingsat periods nestingsites, did not spendtime away, but de- of prey abundance. partedabruptly. Two to threedays prior to their Molting.--Observationson molting (n = 8 fe- departure, the other young spent time away: males)was limited to the breeding season,and 12% (female) and 16% (male) at one site; 43% indicated that breeding and molting over- (female)and 37% (male) at the second.The ages lapped. Early in the nestling period four fe- of young in 1 nestingsite were 64 days(female), maleswere missingeither 1-4 primariesor tail 68 days(male), and 72 days(male) when they feathers,or both. In somefemales molting may departed. At the other nesting site, young de- begin earlier, i.e. after egg-laying.One female partedat 62 days(male), 64 days(female), and beganto molt primaries5 daysafter clutchcom- 68 days (male). pletion. Three other femaleswere missingtail There was a strong correlation between de- or wing feathers(3-7) during the fledging pe- creasein the prey-delivery rate and departure riod. We believe that molt in females is slow of young from the nest areas. Fledglings in 1 and extendsperhaps from 4-6 months. Breed- nestresponded to decreasein prey-deliveryrate ing and molting also overlappedin a Sharp- by spendingless time in the nestarea (Fig. 3a). shinned Hawk population in northeasternOr- Decline of prey deliverieswas abrupt, and was egon(Henny et al. 1985).Females molted more stoppedaltogether 5 daysbefore the fledglings than 60% of their primaries by mid-July, sug- departed.However, the fledglingsdid not leave gestingthat molting beganshortly after clutch when prey deliveriesstopped but graduallyre- completion. ducedtime spentin the nestarea. To the extent Reproductivesuccess.--From 1978-1982 and in the bird densities in the areas censused can be 1985,105 eggs were laid in 40 nests,an average extrapolatedto the homerange of thispair, prey clutch size of 2.6 (Table 6). Two nests were at- abundanceincreased during the period when tended by non-laying pairs. Of 105 eggs 63% prey deliveries decreased and eventually hatched and 47% of the nestlingsfledged. A stopped(Fig. 3b). total of 0.8 young fledged/breeding attempt. Adult and young did not stay togetherafter Productivitywas 0.9 and nest success29%. All the latter departed.We visited 2 nestingsites nesting attempts by immature-plumagedfe- in 1982 and found the adults present, calling males failed (n = 4). and flying, althoughthe younghad left. Adults Reproductivesuccess varied considerablybe- normally entered nestingsites quietly when tween years(Table 6). We excludedthe small young were present. number of nestssampled in 1978. All repro- Egg-layingand hatching occurredover ex- ductive successparameters, with the exception tended periods due to laying and hatching of of the proportion of eggshatched, were lower second clutches. Fledging occurred over a in 1980and 1981.Productivity and nestsuccess 656 DœLANNO¾AND CRVZ [Auk, Vol. 105

QUININA 1982 •, 250. ß

$ 7 • 0• .100 200. •z 150

LUg o4 I•Egg loving• .2o d n-.27 / z 50. . Hatching,.• n=18 - I

(a) 27 29 32 34 37 39 .• 14.Fledgin n--8 J' F•M•A•M•J •J•A •S•O•N 'D • DAYS SINCE FLEDGING Fig. 4. Timing of Sharp-shinnedHawk breeding cycle relative to density of avian prey in Maricao forest(1981). Egg laying and hatchingperiods include secondclutches. There were no fledgingsfrom second clutches.

(73%) were the most important causeof nest failures. Seven of 11 desertions were of second nestingattempts. Nest failuresrelated to deliberate human harassment (20%) were second in (b) MAYJUNE JULY AUGUST importanceduring incubation. Warble fly (Phi- (1982) lornis sp., Diptera, Muscidae) parasitism accounted for most (69%) nest failures during Fig. 3. (a) Relationshipbetween departureof 3 Sharp-shinnedHawk young from nest area (open nestlingstage. Warble fly larvae feed subcuta- squares)and prey-deliveryrate (solid squares). Num- neouslyand causedamage to tissuesof nest- bers above open squaresare hours of observations. lings,affect growth and development,and kill (b) Bird-preydensity in latterpart of breedingseason. the host (Arendt 1985a,b; Uhazy and Arendt 1986). Nestling predation was secondin im- portance(15%). were considerablyhigher in 1979, 1982, and 1985,and highestin 1982.The numberof fledg- DISCUSSION lings/breedingattempt was also highest in 1982. However, reproductiveoutput was highest in Courtshipand territoriality.--The courtship and 1985. territorial behavior of the Puerto Rican Sharp- We comparednest successand averagenum- shinnedHawk did not differ significantlyfrom ber of fledglings produced between first and other smallAccipiter hawks (Brown 1976,New- secondnesting attempts. Nest successwas 36% ton 1979). The "undulating flight display" of (n = 33 nests)in first attemptsand 0%in second malesprior to pair formationmight serveboth nesting attempts(n = 9 nests).First attempts to attractpotential mates and give an assertive produced0.9 fledglingsand secondattempts message.When agonistic behavior between none. malesduring a territorialconflict reached high We determined nest failures in relation to intensitylevels, they renderedtheir talonsin- nesting stage of first and secondnesting at- effectiveby grapplingeach other. This ritual- tempts.Nest failuresduring the nestlingstage ized aggressionallowed the contestantsto as- were similar (36% in'the first attemptsand 33% sesstheir strengthswithout inflicting damage. in second nesting attempts). In contrast, nest Territory possessionreduced disturbance failures during the egg stage were approxi- during pair formation.The territorialconflicts mately 3 times higher in secondnesting at- in the Maricao forestsuggest that nesting sites tempts(67%) than in firstattempts (21%). Causes were in short supply or that there was an un- of nest failures in relation to stage of repro- balanced adult sex ratio (more males than fe- duction were determined in 28 nests and re- males).Unfortunately, we were unable to dis- nests (Table 7). During incubation, desertions tinguishthese to possibilities.Effects of intruder October1988] Sharp-shinnedHawk BreedingBiology 657

TA13I•E6. Reproductivesuccess of Sharp-shinnedHawks.

No. No. No. Mean No. (%) No. (%) Fledglings/ Fledglings/ Nest nests active eggs clutch eggs young breeding territorial successa Year studied nestsa laid size hatched fledged attemptb pair (n)c (%) 1978 2 2 6 3.0 3 (50) 0 (0) 0 0 (2) 0 1979 7 7 18 2.6 10 (56) 9 (90) 1.3 1.5 (6) 43 1980 6 6 14 2.3 8 (57) 1 (13) 0.2 0.3 (3) 17 1981 11 11 29 2.6 18 (62) 1 (6) 0.1 0.1 (8) 9 1982 6 6 16 2.7 15 (94) 9 (60) 1.5 1.8 (5) 50 1985 10 8 22 2.8 12 (55) 11 (92) 1.4 1.2 (9) 40 Total 42 40 105 2.6 66 (63) 31 (47) 0.8 0.9 (33) 29

Active nest defined as a nest with at leastone egg. Breedingattempt refersto a clutch initiated (first nestsand renests). n = total number of breeding and nonbreeding pairs. Nest successis the proportion of neststhat fledged at leastone young. males on the breeding activities and fitnessof dance, but females had to reach optimal body pairs were not determined. condition to lay during relatively low prey Durationand timing of thebreeding cycle.--The abundance.Perhaps females need a longer pre- breeding cycle in Puerto Rico was approxi- laying period to reachoptimal body condition mately 2 months longer than in Oregon and during low prey abundancethan high prey Utah (Fig. 5). Similarly, tropical passerines abundance.Body condition of the femaleis cru- (Ricklefs 1969a) and other raptors of compara- cial (Romanoff and Romanoff 1949, Ricklefs 1974, ble size and similar trophic requirements also Alisaukasand Ankney 1985,Astheimer and Grau have protracted breeding cycles compared to 1985). In the Eurasian Sparrowhawk only fe- their temperate-latitude counterparts (Brown malesthat gain masssubsequently lay (Newton 1976;Newton 1977,1979; Wiley and Wiley 1981; 1986). The reserves buffer females against er- Mader 1981,1982).Differences between tropical ratic prey delivery by males and allow unin- and temperateavian groupsstem primarily from terrupted incubation and feeding of young. differences in the length of time required to Tawny Owl (Strix aluco)showed similar differ- completevarious stagesof the breeding cycle. encesin massbetween laying and non-laying However, duration of incubation, nestling, and females (Hirons 1976). Some albatrosses,geese, fledglingstages is aboutthe samein PuertoRico, and penguinsarrive on their breeding grounds Oregon, and Utah. The elapsedtime from oc- when feeding conditions are poor, and have cupancyof nesting sitesto initiation of laying long breeding seasons.Food intake is reduced, accounted for the differences in the duration of and body reservesare an important sourceof breedingcycles. Early occupancyof the breed- energy and nutrients for pre- and post-laying ing grounds in Puerto Rico may be advanta- activitiesand egg synthesis(Frings and Frings geousif Sharp-shinnedHawks could detectspa- 1961,Barry 1962,Fisher 1967, Ryder 1970,War- tial and temporal changes in distribution and ham 1974). abundanceof prey resources.This may be par- It is possiblethat the breeding seasonin Puer- ticularly important if this information was a to Ricowas restricted to a relativelybrief period proximate cue to initiate egg laying. (dry season)by low food availability and ex- The fledging period in Sharp-shinnedHawks tremely high precipitation in the wet season. was synchronizedwith the peak of prey abun- Unfortunately, data on prey abundancewere

TABLE7. Causesand timing of Sharp-shinnedHawk nestfailures.

Time of Desertion Desertion of Predation Predation Human failure of eggsa nestlingsa on eggs on nestlings Warblefly relatedb Total Pre-hatching 11 (73%) -- 1 (7%) -- -- 3 (20%) 15 Post-hatching -- 1 (8%) -- 2 (15%) 9 (69%) 1 (8%) 13 Direct observationsconfirmed abandonment of viable eggs or young. Human related refers to deliberate human harassment of nests, their contents or adults which resulted in nest failure. 658 DEr•qNO¾AND CRVZ [Auk,Vol. 105

• ARRIVAL-NEST-BUILDING encesin growth rates have been found in other • INCUBATION dimorphic raptors (Schnell 1958, Moss 1979, Pi- cozzi 1980).Male Sharp-shinnedHawk in Puer- [• NESTLING to Rico became behaviorally advanced and •]• FLEDGLING feathered sooner than females. They left the nest earlier and developed flight skills sooner. •111111•/1111111 132 •] ao I[11• I[ II ,.4 PUERTO RICO In mostdimorphic raptor speciesfor which data OREGON are available, malesfledge earlier than females

UTAH 117 (Newton 1979). These adaptationsmight help minimize competitionof the larger femaleswith UTAH 107 the smaller male siblings. We found no infor- 3•3 6• 9• 1•0 1dO 18•) mation on Sharp-shinned Hawk growth rates DAYS in temperateNorth America. Eaglespecies vary Fig. 5. Duration of Sharp-shinnedHawk breeding in their growth pattern, not becauseof sibling cycle in Puerto Rico and 3 populations in North competitionfor food asproposed by Werschkul America. Number inside breeding stage represents and Jackson(1979), but because of selection to its duration. Data for Puerto Rico basedon sample of reduce peak energy requirementsof nestlings 13 nests, Oregon on 12 nests (Reynolds 1978), and (Bortolotti 1986). Utah on 7 and 34 nests(Hennessy 1978 and Platt 1973, Young hawks continued to grow after fledg- respectively). ing and this apparently influenced the length of the dependencyperiod afterwards.At fledging, young were slightly heavier than adults. not availablefor the last quarter of the year in Wing chord and tail lengths were approxi- Maricao.If there were a period of reducedabun- mately 50% shorter than those of adults. Allo- danceor availabilityof prey in the last quarter metric growth of body parts in young limited of the year,it mayhave prevented the temporal the flying capabilities at fledging. Delayed separation of breeding and molting, which growth of wings and tail in young hawksforced overlapped in Maricao forest. The hawks ap- them to develop their flight skills slowly and peared to have a low rate of molt that lasted progressively.This is particularlyimportant be- many months,which could reducethe energy causeSharp-shinned Hawks feed primarily on requirementsand insure adequateinsulation elusiveavian prey. During the dependencype- and flight performance.Egg laying at 3 Sharp- riod, young hawks pursued birds, butterflies, shinned Hawk nests in eastern Puerto Rico (Lu- and captured lizards. Young Peregrine Falcon quillo Forest)was also in the dry season(Snyder (Falcoperegrinus) learned to discriminatethrough and Wiley 1979).Overall countsof smallbirds trial and error which specieswere suitable as in that forest showed strong seasonalitywith a prey and which were most profitable to hunt majorpeak in spring,a drop in summer,a lesser (Sherrod 1983). Mueller and Berger (1970) peak in autumn, and another drop in winter. showed that young North American Sharp- Heavy rainfall might interfere with foraging shinned Hawks attackedbirds too large assuit- acti.vitiesof the hawks,which feed on relatively able prey more often than adults and attributed elusiveavian prey. In fact, severerainfall was this difference to lack of experience. Newton suggestedas a cause of Puerto Rican Sharp- (1986) reported young EurasianSparrowhawk shinnedHawk nestfailures in Luquillo (Snyder females attacking bird prey larger than them- and Wiley 1976)and Toro Negro (Cruz and De- selvesand suggestedthat learning consistedof lannoyMS) forests.In GreatBritain, rainfall was restrictingattacks to smaller and more manage- the secondmost frequent cause of mortalityof able prey. Learning presumablyplays an im- young Eurasian Sparrowhawks during the portant role in the development of Sharp- breedingseason (Moss 1979).Rainfall affected shinned Hawk hunting skills. prey delivery and forcedthe femalesto hunt, Other investigatorshave reported a trend of which left the young unattendedand resulted declining prey deliveries towards the end of in prolonged exposureand death. breeding seasonsimilar to that of the Sharp- Developmentand dispersaL--Allgrowth pa- shinned Hawk. Snyder and Wiley (1976) ob- rameters examined indicated that male nest- served declining prey deliveries late in the lings grew faster than females.Sexual differ- breeding seasonat 2 of 3 nestsin Arizona and October 1988] Sharp-shinnedHawk BreedingBiology 659

T^nI•E8. Reproductivesuccess of Sharp-shinnedHawks in PuertoRico and North America.

PuertoRico Oregona Utahb Utahc Wyomingd Mean clutch size 2.6 (105/40) 4.6 (23/5) 4.3 (146/34) -- 3.5 (7/2) % eggshatched (hatchingsuccess) 63 (66/105) 70 (16/23) -- -- 100 (7/7) % of hatched chicksfledged (nestlingsurvival) 47 (31/66) 81 (13/16) -- -- 100 (7/7) % successfulnests 29 (12/42) 92 (11/12) -- 62 (58/94) 100 (2/2) Fledglings/breedingattempt 0.8(31/40) 2.7(30/11) -- -- 3.5(7/2) Fledglings/nest 0.7(31/42) 2.5(30/12) 4.5(9/2) 2.1(197/94) 2.5(7/2) Fledglings/territorialpair 0.9(31/33) 2.7(30/11) -- -- 3.5(7/2) Reynoldsand Wight (1978). Platt (1973). Hennessy(1978). Craigheadand Craighead(1956). felt thesenests were stressedby food shortage. Although the data on adult mortality are lim- Mueller et al. (1981) reported 65% fewer prey ited, someindividuals were still alive 3 yr and deliveries/h and 63% fewer g/h to a nest to- up to 5 yr after being banded.Other indirect wards the end of the dependencyperiod and evidence suggestiveof low adult mortality is attributed the decline to reduced hunting by that only 3 of 42 nesting femaleswere in im- adults, rather than to depleted prey resources. matureplumage. No immature-plumagedmales Alternatively, the gradual decreaseof prey occupiednesting sites. We surmisethat recruit- deliveries could have been a strategy of the ment of reproductiveindividuals into the pop- adultsto force the young to becomeindepen- ulation is low. There was no evidence that the dent. This proposition is consistentwith the Sharp-shinnedHawk population in Maricao is parent-offspringconflict theory developed by maintainedby an influx of individuals from Trivers (1974). The fledglings,in order to max- other populations.Individuals bandedin Toro imizetheir inclusive fitness, may dema•td more Negro and Luquillo forestshave not been ob- parental investmentthan what the adultscould served in Maricao. Most lands adjacentto the possiblyprovide. Therefore, "the optimal strat- Maricao forest are under cultivation or in early egy should involve flexibility in the behavior secondarygrowth and may not be suitablefor of adults with parental care being prolonged nesting. when food is scarce" (Mueller et al. 1981: 89). In general,birds on tropical islandsand in However, the length of parental care also de- mainlandregions have lower fecundityand re- pends on whether or not the population is mi- productive successthan their counterpartsin gratory.Several studies have suggestedthat pa- temperatelatitudes (Ricklefs 1969b, Klomp 1970, rental "meanness"(i.e. indifference,aggression, Cody 1971,Skutch 1976, Crowell and Rothstein or both) is an important factor influencing off- 1981). We comparedreproductive variables of springindependence (Trivers 1974, Wilson 1975, Sharp-shinnedHawks in Puerto Ricowith tem- Davies 1978). We do not know where immature perate North American areas (Oregon, Utah, individuals establishedresidency. Wyoming)to determineif the generaltropical- Populationecology.--Despite the low repro- temperatereproductive trend held. In all vari- ductive successof the Sharp-shinnedHawk in ablesexamined, the averagesin PuertoRico were Maricao forest, there is no indication that this lower (Table 8). Egg lossesin Puerto Rico were population is declining. We censusedan area primarily due to desertions,while infertility, of 29.1 km• and obtained breeding densities of deathof embryos,and eggbreakage caused egg 1.06 individuals/km 2 in 1981 and 1.03 individ- lossesin Oregon,perhaps due to high levels of uals/km 2 in 1985 (unpubl. data). In addition, pesticides(Reynolds and Wight 1978).In the although reproductivesuccess was very low at Maricaopopulation some females may have suf- many nesting sites, the reoccupancyrate was ficientbody reserves to produceeggs, but they relatively high. A low reoccupancyrate might then experienceshortage of body reservesand indicatehigh adult mortality and very little re- abort nestingattempts. Low body reservesand cruitment,or emigrationinto adjacenthabitats. decliningfood resourceswere likely causesof 660 DELANNOYAND CRUZ [Auk, Vol. 105 desertionsand were particularly common in LITERATURE CITED secondnesting attempts. The high incidenceof ALIS^UKAS, R. T., & C. D. ANKNEY. 1985. Nutrient nest desertionsduring incubation resulted in reservesand the energeticsof reproduction in low hatching successof this population. American Coots. Auk 102: 133-144. Lower fecundity in Puerto Rico could be re- ARENDT,W. J. 1985a. Philornisectoparasitism of lated to high adult life expectancyin this pop- Pearly-eyedThrashers. I. Impact on growth and ulation. We have provided evidence that adult development of nestlings.Auk 102: 270-280. survivalwas relatively high, recruitmentto the --. 1985b. Philornisectoparasitism of Pearly-eyed breeding population was slow, and the popu- Thrashers.II. Effectson adultsand reproduction. lation was at carrying capacitywith existing Auk 102: 281-292. nesting habitat. As suggestedby Pianka (1978: ASTHEIMER,L. B., & C. R. GRAU. 1985. The timing 128), "current reproductiveeffort should be in- and energeticconsequences of egg formation in the Ad&lie Penguin. Condor 87: 256-268. versely proportional to adult life expectancy." BARRY,T. W. 1962. Effect of late season on Atlantic Some pairs in Maricao forest renested after Brant reproduction.J. Wildl. Manage. 26: 19-26. losing their eggsor nestlings.This habit may BENSON,D. W., R. K. BROOKE,R. J. DOWSETT,& M.P. help to offset the low fecundity of the popu- IRWINß 1971. The birds of Zambia. London, Col- lation. However, none of the second nesting lins Publishing Co. attempts fledged young. The Savanna Hawk BENT, A. C. 1937. Life histories of North American (Buteogallusmeridionalis), another tropical raptor birds of prey, part 1. U.S. Natl. Mus. Bull. 167. with low fecundity and capacityto renest, had BORTOLOTTI,G.R. 1986. Evolution of growth rates 40%success on secondnesting attempts (Mader in eagles:sibling competitionvs. energy consid- 1982). It is possiblethat in some years Sharp- erations. Ecology 67: 182-194. shinned Hawks in Puerto Rico have better suc- BROWN,L. 1976. Birds of prey: their biology and cesson second nesting attempts than during ecology.New York, A. W. Publishers,Inc. our study period. Renestingfollowing lossof CODY,M. L. 1971. Ecologicalaspects of reproduc- nestlingshas not been reportedfor the Sharp- tion. Pp. 461-512 in Avian biology, vol. 1 (D. S. shinned Hawk in North America. Farner and J.R. King, Eds.).New York, Academic Press. CRAiGHEADJ., & F. CRAIGHEAD. 1956. Hawks, owls, ACKNOWLEDGMENTS and wildlife. Harrisburg, Pennsylvania, Stack- pole Co. We are grateful to J. A. Rivera,S. Vidr6, S. Graves, CROWELL,K. L., & S. I. ROTHSTEIN. 1981. Clutch sizes and A. Gravesfor help in different capacitieswith and breeding strategies among Bermudan and the fieldwork. H. Diaz-Soltero, R. Schmidt, and L. North American passerines.Ibis 123: 42-50. S•nchez, Department of Natural Resourcesof the CRUZ,A., & C. A. DELANNOY.1984. Ecologyof the Commonwealth of Puerto Rico, generouslygranted Elfin Woods Warbler (Dendroicaangelae). I. Dis- permissionto work on property under their jurisdic- tion and providedliving facilities.F. Thompson,Re- tribution, habitat usageand population densities. Caribbean J. Sci. 20: 89-96. searchEntomologist, Systematic Entomology Labo- ratory, United StatesDepartment of Agriculture,and D^VIES,N.B. 1978. Parentalmeaness and offspring S. Medina-Gaud, ResearchEntomologist Agricultural independence:an experiment with hand-reared ExperimentalStation, University of PuertoRico, iden- Great Tits, Parusmajor. Ibis 120: 509-514. tified insect specimens.Our researchwas supported DEVRIES, T. 1975. The breedingbiology of the Ga- by a contractfrom the United StatesFish and Wildlife lfipagosHawk, Buteogalapagoensis. Le Gerfaut 65: Serviceno. 14-16-0004-82-047.Additional supportwas 29-57. providedby grantsfrom the University of Colorado, EMLEN,J.T. 1971. Population densitiesof birds de- (Kathy Lichty Memorial Fund), National Academyof rived from transect counts. Auk 88: 323-342. Sciences,(Joseph Henry Fund), American Ornithol- ß 1977. Estimating breeding seasonbird den- ogists'Union (AlexanderWetmore Award), American sities from transect counts. Auk 94: 455-468. Museum of Natural History (Frank M. Chapman EWEL,J. J., & J. L. WHITMORE.1973. The ecological Fund), and University of Puerto Rico (Presidential life zones of Puerto Rico and the U.S. Virgin Award). To all these institutionswe are grateful. We Islands.Forest Service Research Paper ITF-18. thank J. W. Arendt, C. E. Bock,C. Ortega, R. T. Reyn- FAABORG,J., T. DE VRIES, C. B. PATTERSON,& C. g. olds, and E. Santana for comments on an earlier ver- GRIFFIN.1980. Preliminary observationson the sion of this paper. Clayton M. White, Paul Matray, occurrenceand evolution of polyandry in the and an anonymousreviewer madecomments that im- Gal•pagosHawk (Buteogalapagoensis).Auk 97: 581- proved the manuscript. 590. October1988] Sharp-shinnedHawk Breeding Biology 661

FFRENCH,R.P. 1980. The breeding of the Pearl Kite in two groups of coexistingAccipiters. Ph.D. dis- in Trinidad. Living Bird 19: 121-131. sertation, Corvallis, Oregon, Oregon State Uni- FISHERßH. I. 1967. Body weights in Laysan Alba- versity. trosses, Diomeda immutabilis.Ibis 109: 373-382. 1983. Management of western coniferous FRINGS,H., & M. FRINGS. 1961. Some biometric stud- foresthabitat for nesting Accipiterhawks. USDA ies on the albatrossesof Midway Atoll. Condor ForestService Gen. Tech. Rep. RM 107. Fort Col- 63: 304-312. lins,Colorado, Rocky Mountain Forestand Range HENNmSY,S. P. 1978. Ecologicalrelationship of Ac- Exp. Station. cipitersin northern Utah, with emphasison the ß & E. C. MESLOW.1984. Partitioning of food effectsof human disturbance.M.S. thesis,Logan, and niche characteristicsof coexistingAccipiter Utah, Utah State University. during breeding. Auk 101: 761-779. HENNY, C., R. A. OLSON, & T. L. FLEMING. 1985. ß& H. M. WIGHr. 1978. Distribution, density, Breeding chronology, molt, and measurements productivityof Accipiterhawks breeding in Or- of Accipiterhawks in northeasternOregon. J. Field egon. Wilson Bull. 90: 182-196. Ornithol. 56: 97-112. RICKLEFS,R. E. 1967. A graphicalmethod of fitting HIRONS,G. 1976. A population study of the Tawny equationsto growth curves.Ecology 48: 978-983. Owl and its main prey speciesin woodlands.Ph.D. 1969a. The nesting cycle of song-birdsin dissertation,England, Oxford University. tropical and temperate regions. Living Bird 8: KLOMP, H. 1970. The determination of clutch size 165-175. in birds. A review. Ardea 58: 1-124. 1969b. An analysisof nestingmortality in LIVERSIDGE,R. 1962. The breeding biology of the birds. Smithson. Contrib. Zool. 9: 1-48. Little Sparrowhawk,Accipiter minullus. Ibis 104: 1974. Energeticsof reproduction in birds. 399-406. Pp. 152-292 in Avian energetics(R. A. Paynter, MADER,W.J. 1981. Notes on nestingraptors in the Ed.). CambridgeßMassachusetts, Publ. Nuttall Llanos of Venezuela. Condor 84: 48-51. Ornithol. Club No. 15. 1982. Ecology and breeding habits of the ROMANOFF,A. L., & A. J. ROMANOFF. 1949. The Avian Savanna Hawk in the Llanos of Venezuela. Con- Egg.New York, JohnWiley and Sons,Inc. dor 84: 261-271. RYDER,J.P. 1970. A possiblefactor in the evolution MossßD. 1979. Growth of nestling Sparrowhawks, of clutch size in Ross' Goose. Wilson Bull. 82: 5- 13. Accipiternisus. J. Zool. 187: 297-314. MUELLERßH. D., & D. D. BERGER.1970. Prey pref- SCHNELL,J.H. 1958. Nesting behavior and food habits of Goshawks in the Sierra Nevada of Califor- erencesin the Sharp-shinnedHawk: the rolesof nia. Condor 60: 377-403. sex,experience, and motivation.Auk 87:452-457. ß N. S. MUELLER, & P. G. PARKER. 1981. Ob- SHERROD,S. K. 1983. Behaviourof fledgling pere- servationof a brood of Sharp-shinnedHawk in grines. Ithaca, New York, The Peregrine Fund. Ontario, with comments on functions of sexual SKUTCH,A. F. 1976. Parent birds and their young. Austin, Univ. Texas Press. dimorphism.Wilson Bull. 93: 85-92. NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRA- SMEENK,C. 1974. Comparative-ecologicalstudies of someeast African birds of prey. Ardea 62: 1-97. TION. 1971-1982. Climatological data, Puerto ß & N. SMEENK-ENSERINK. 1975. Observations Ricoand the U.S. Virgin Islands.Asheville, North Carolina, National Climatic Center, U.S. Depart- of the Pale ChantingGoshawk, Milierax poliop- ment of Commerce. terus,with comparativenotes on the Gabar Gos- hawk, Micronisusgabar. Ardea 63: 93-115. NEWTON,I. 1977. Breedingstrategies in birdsof prey. ß & --. 1977. Observations of the Shrika, Living Bird 16: 51-82. Accipiterbadius, in Nigeria. Ardea 65: 148-164. 1979. Population ecologyof raptors.Vet- SNYDER,N., &: J. W. WILEY. 1976. Sexual size dimor- million, South Dakota, Buteo Books, Inc. phism in hawks and owls in North America. Or- 1986. The Sparrowhawk. CaRon, England, nithol. Monogr. 20. T. and A.D. Poyser. SOKALßR. R., & 1. ROHLF. 1981. Biometry: the prin- PIANKA,E. R. 1978. Evolutionary ecology. Second ciples and practiceof statisticsin biological re- Edition. New York, Harper and Row, Publishers. search. San Francisco, W. H. Freeman Co. PICOZZI,N. 1980. Food, growth, survival and sex THIOLLAY,J. M. 1975. Les rapaces d'une zone de ratio of nestling Hen HarriersßCircus cyaneus, in contact savane for•t en C6te-d-Ivoire. Alauda 43: Orkney. Ornis Scandinavica11: 1-11. 75-102; 347-416. PLATT, J. B. 1973. Habitat and time utilization of a TRIVERS,R. L. 1974. Parent-offspringconflict. Am. pair of nesting Sharp-shinnedHawkß Accipiter Zool. 14: 249-264. striatusvelox. M.S. thesis,Provo, Utah, Brigham UHAZY,L. S., & W. I. ARENDT. 1986. Pathogenesis Young University. associatedwith Philomid myiasis(Diptera: Mus- REYNOLDS,R.T. 1978. Foodand habitat partitioning cidae)on nestlingPearly-eyed Thrashers (Aves: 662 DEL.•INO¾ant) CRVZ [Auk,Vol. 105

Mimidae) in the Luquillo rain forest,Puerto Rico. WILEY,J. W., & B. WILEY. 1981. Breedingseason ecol- J. Wildl. Diseases 22: 224-237. ogyand behavior of Ridgway'sHawk, Buteoridg- WARHAM,J. 1974. The Fiordland Crested Penguin, wayi. Condor 83: 132-151. Eudyptespachyrynchus. Ibis 116: 1-27. WILSON,E. O. 1975. Sociobiology.Massachusetts, WERSCHKUL,D. F., & J. A. JACKSON.1979. Sibling Belknap Press. competition and arian growth rates.Ibis 121:97- 102.

From the review (1888, Auk 5: 414) of G. Trumbull's "Names and Portraits of Birds Which Interest Gunnerswith Descriptionsin LanguageUnderstanding of the People" (1888.New York, Harper and Brothers.viii + 222 pp. [no price given]):

"Vernacular Ornithology.--This is a wonderful North America--the natatorial, gallinaceous,limi- world of checks,balances, compensations, and reac- coline and paludicole birds ordinarily pursued, for tionary running-gear. For example, the A.O.U. Com- sport by 'that helplessbut interestingcreature, "the mittee has upsetall the technicalnames of birds that true sportsman,"'or for profit by 'our gunners,a class could thus hardly be dealt with, and Mr. Trumbull of men who earn a livelihood by shooting birds.' has set up all the vernacular names that could be These we find to be sixty-one in number. They are treatedunderstandingly. Thus ornithology fattens and first named in strict accordwith the rules and regu- flourishes, as on loaves and fishes; for has not our lations for such casesand provided by the A.O.U. author wrought a veritable miracle; namely, the fill- Committee,the dogmasof which deathlessdoers of ing of a 'long-felt want'? (Not that any one has ac- deedsnomenclatural are acceptedby Mr. Trumbull tually felt that want until the void has been filled; with orthodoxhumility. Then comesa brief descrip- but it existed,and only neededfilling to be felt and tion, in language'understanded of the people,' to- grow by what it fed upon. Even ornithologists,how- gether with a statementof habitat in each case,the ever hopelesslymired down in the mazes of their range being usually drawn from the same fountain 'shoptalk,'as our irreverent friend terms their tech- of infallibility whencethe sacredscientific names is- nical vocabulary,may find in this book muchto their sue:for in the beginning was the word, and the word profit. Seeingthat theirsis not the only languagethat was with the Committee. With these data comes a is weighted with synonymaticwoe, they may take portrait in each case--a striking silhouette,or sym- heart again. Many of them have 'viewed with alarm' phony in black and white, struckby the well-known asthe politicianssay, the greatload of wordy rubbish hand of Mr. Edwin Sheppard,who has made better that our sciencecarries; the spectacleof a bird with likenessesof more birds than any other American half a dozen generic, a dozen specific names, and artist now living. Having thus marked down his bird, several dozen combinations of these two terms has a so to speak,Mr. Trumbull proceedsto bag his game chasteningeffect upon the mind. But now, with risen with a wealth and ingenuity of devicethat exciteour spirits,we can 'point with pride,' like statesmen,to unboundedadmiration. It is truly an infinite variety the synonymaticconfusion worse confounded which that neither agecan stalenor customwither--a boun- our mother tongue offersto consoleus, if not to ab- teousness,a plentitude, a very plethora,the fullness solve us from our sins. For here we have a thousand whereof is exhaustless.Allah is said to be invoked by and more names for three-score birds! Et tu Brute, Mr. the piousMussulman under ninety and nine aliases, Trumbull? and history but repeatsitself in the myrionymy of "But to be serious, as befits the rich embarrassment the game birds of America. A thousandnames, for with which the author endows us, let us examine this three-scorebirds, by a single prophet!"...--E.C. remarkablework. It treatsall the gamebirdsof Eastern