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The Curacao Barn Owl: Status and Diet, 1987-1989

ADOLPHE O. DEBROT1, JOHN A. DE FREITAS1,4, ALEWIJN BROUWER2, ANDMARTEN VAN MARWIJK KOOY3.

1CARMABI Foundation, P.O. Box 2090, Piscaderabaai, Curacao, Netherlands Antilles.2Institute for Systematics and Population Biology (Zoological Museum), University of Amsterdam, P.O. Box 94766,

1090 GT Amsterdam, The Netherlands.Present address: BugelHajema bv, Vaart nz 48-50, P.O. Box 274, 9400 AG Assen, The Netherlands.

3Department of Terrestrial Ecology and Nature Conservation, Wageningen Agricultural University, Bornsesteeg 69,6708 PD Wageningen, The Netherlands.

Present address: Utrechtsewg 65, 3721 HA De Bilt, The Netherlands4Corresponding author.

ABSTRACT.We examined the status and diet of the Barn Owl, Tyto alba Scopoli, on the dry, southern

Caribbean island of Curacao. Thorough surveys of natural (limestone plateau escarpments, caves, seaboardcliffs) and anthropogenic habitats (ruins, wells, attics) during 1987 and 1989, yielded 42 confirmed active Barn

Owl sites (15 nest sites, 16 pair roosts, 11 other roosts of regular use). The total estimated population

(1987-1989) was about 75 adult birds (31 pairs and additional individual birds). Breeding and daytime roostsites were predominantly located in fissures, cavities, and ledges along the escarpments of limestone pla-

teaus; even though the species was also documented in two caves, a seaboard limestone cliff slope, and a fewanthropogenic sites. It appears that nesting at caves and old plantation homes has greatly declined due to

intensified disturbance. During the dry year of 1987, laying took place in the rainy season (October-December). In response to extended end-of-year rains in 1988, several sites achieved two broods in 1989. The

main prey during both survey periods were introduced rodents, yet major differences in the importance ofspecific prey categories were evident. The results also indicate a high abundance of birds in the diet, as well

as a high spatial and temporal variability in food composition.

INTRODUCTION

The Barn Owl, Tyto alba Scopoli, is a cos-mopolitan species represented almost ev-erywhere in the tropics and temperate zone(Bunn et al., 1982; Voous, 1983). Due to itsextraordinary colonizing abilities the spe-cies is often found on isolated islands. Littleis known about the Curacao Barn Owl, asubspecies occurring only on the island ofCuracao (T. alba bargei Hartert) and charac-terized by its small size and light coloration(Voous, 1957, 1983). Sight observations andone recent specimen that confirms the pres-ence of Barn Owls on the nearby island of

Bonaire, appear to represent a differentsubspecies (T. Prins, University of Amster-dam, pers. comm.). Until 1985, the totalnumber of Barn Owls on Curacao was es-timated as probably less than 20 pairs

based on incidental observations (Voous,1985).

The purpose of this study was to provide

an initial assessment of the status of the

species, as well as information on other as-pects of its biology, especially diet.

MATERIALS AND METHODS

Curacao lies in the southern CaribbeanSea, about 70 km north of Venezuela. Theisland consists of a largely basaltic interiorrimmed by coralline limestone plateausand escarpments in the coastal areas. Totalsurface area is approximately 444 km2 andthe climate is semi-arid. Rainfall averagesabout 550 mm y1, half of which occurs in

the rainy season from October to December(Meteorological Service, 1982). The vegeta-tion has been changed by centuries of in-tensive grazing and wood harvest, and forthe large part consists of deciduous and ev-ergreen secondary thorny woodland andscrub.The human population has fluctu-ated around 140,000 for the last two de-

Caribbean Journal of Science, Vol. 37, No. 3-4, 185-193, 2001Copyright 2001 College of Arts and SciencesUniversity of Puerto Rico, Mayaguez

185


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cades. Most habitation and industry is con-centrated in the east-central third of theisland.

Natural Barn Owl roosts and nest sites inCuracao are almost exclusively limited toescarpments of limestone plateaus andcaves, which occur in a narrow band cir-cling the island. Breeding and roosting sitestend to be used over many generations, andare relatively easy to detect based on regur-gitate remains or other indicators such asexcrement and feathers. Thus, the area to

be searched was limited and the likelihoodof detection was high, such that a detailedsurvey of the Barn Owl population of theisland is workable.

During 1987 (June 1987-January 1988),the escarpments of the limestone plateausand associated caves and boulders of abouttwo thirds of the island (central and easternparts) were systematically searched fortraces of Barn Owls. In addition, severalpreviously known sites, as well as selectedhigh-potential sites, on the west side of theisland were visited. Barn Owls occasionallyuse abandoned, undisturbed man-madestructures in rural and urban areas (Voous,1983). Hence, attics of abandoned build-ings, ruins, abandoned mining sites, andwells were also visited, as were seaboardcliffs which overhang the water.

To complete the list of Barn Owl sites forthe western side of the island, systematicsurveys of all limestone escarpments onthis area were conducted in 1989 (March-

July 1989 and October 1989-January 1990).Also, 29 of the 39 more accessible sites stud-ied in the 1987 survey period were revisitedto assess roosting and breeding activity.Nine of the ten sites not revisited are on theeasternmost part of the island. The nativewords seru, berg and roi often form part ofthe site names. The first two connote hill,while the latter refers to gully.

Sites of regular Barn Owl use were clas-

sified, based on the highest ranked usageobserved, as either a breeding site (B), apair roosting site (P), or a roosting site (R)of extended use where only fresh regurgi-tates were found or sightings of solitaryowls were made. Sites of incidental usewere not included for analysis. The level ofreproductive activity was expressed as a

site nest-to-pair ratio (%) and compared be-tween the 1987 and 1989 seasons by meansof a Chi-square test for independence (Wal-pole and Myers, 1978).

Owls left their roosts 30 min before to 30min after sunset. All roosts and nestingsites with regurgitates, or remains thereof,were visited twice monthly to determine ifthe roosts were active, to look for signs of

breeding activity, and to collect fresh regur-gitates. Chick age was assessed on the basisof plumage development and behavior(Bunn et al., 1982; de Jong, 1983). This al-lowed back-calculation of the time of egglaying.

The number and identity of prey speci-mens in regurgitates were determined permonth for all sites during the 1987-1988 pe-riod. For mammals and reptiles, all skullmaterial was collected and the number ofeach prey species was estimated from themaximum number of left, right, or uppermandibles present. Mammal remains wereidentified using the keys by Husson (1960,1962), reptile remains were identified usinga small reference collection, and bird re-mains were identified by comparison witha small reference collection and specimensfrom the Zoological Museum of Amster-dam. The maximum number of lower orupper mandibles (with or without skull)was used for enumerating avian prey;whereas legs, parts of the abdomen andthorax, or ovipositors were used for insects.Insects were identified to family level be-cause they were less well preserved. Preyitems were identified only to higher taxo-nomic categories for the 1989 survey pe-riod. Comparisons of food composition be-tween pairs and between years were done

by means of the Chi-square test for inde-pendence (Walpole and Myers, 1978).

During the 1987 period, data were ob-tained that allowed a limited assessment ofpotential intra-annual seasonal variation in

prey composition. We selected four owlsites for which data on prey items of at leastfive successive months were available andwhich were located within 2 km or lessfrom a Meteorological Service rainfallmonitoring station. The sites were testedfor a significant linear regression (Walpoleand Myers, 1978) between percentage of ro-

A. O. DEBROT ET AL.186


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dents and precipitation in the previousmonth. All data on precipitation wereobtained from the Meteorological Serviceof the Netherlands Antilles and Aruba. Un-less otherwise stated, average annual rain-fall figures are based on 12 widely distrib-uted rainfall stations with complete datasets.

RESULTS

Population status

During 1987, 37 of 39 documented BarnOwl sites were in use, of which 25 were atleast occupied by pairs and 9 had evidenceof nesting (Fig. 1). Three additional siteswere found during 1989, when 32 siteswere monitored of which 15 were occupied

by pairs and 8 had nests. Assuming nodouble-counting, the combined count of 42active sites (15 documented with nests, 16with a pair, 11 with at least one adult bird)yielded an estimate of 75 adult birds for theisland. At an approximate total island sur-

face area of 444 km2, this translates to apopulation density of about one pair per1200 ha.

Most sites were found in horizontal orvertical fissures in vertical escarpments oron ledges in high, shaded rock overhangsof the limestone plateaus (Fig. 1). Most siteswere found on the eastern half of the is-land, where limestone cliffs are moreprominent. Sites were generally protectedfrom wind, sun, and rain, were 3-6 m abovethe base of the escarpment and allowed un-obstructed flight access. One instance of

birds using a cave was documented (site32). Of the 29 sites visited during both sur-vey periods, 15 were occupied in both pe-riods, 12 were occupied only during thefirst period, and 2 were occupied only dur-ing the second period (Fig. 1).

Use of anthropogenic sites was docu-mented in three cases: a suburban attic thatwas only temporarily occupied, the cov-ered veranda of a little-used country retreaton the rural west side of the island, wherea nest box was subsequently placed andused for nesting (site 1) (Fig. 1), and anabandoned mine shaft (site 30).

FIG. 1. Map of Curacao showing the occurrence of Barn Owl roost and nest sites in relation to limestoneterrace habitat and human habitation. Site numbers are followed by the survey results for the 1987 and 1989

survey seasons. (B) = breeding, (P) = pair, (R) = roost, (NV) = not visited, () = not occupied. Site names andlocations: 1) Villa Stella Maris, 2) E Seru Zjeremi, 3) W Franki, 4) N Seru Largu, 5) N Seru Kabaye, 6) NW SeruPopchi, 7) N Seru Hermanus, 8) E Seru Hermanus, 9) E Roi Katun, 10) N Pestbaai, 11) N Seru Sami, 12) N SeruPretu, 13) N Seri Kura, 14) E Seri Kura, 15) E Seru Mansinga, 16) W Kabrietenberg, 17 N Kabrietenberg, 18) NSeri Boka, 19) boulder SW Tafelberg, 20) S Tafelberg, 21) N Tafelberg, 22) N Tafelberg, 23) N Duivelsklip, 24)N Seri Mainshi, 25) S Seri Boka, 26) S Seru Stela, 27) N Seri Kibra Pika, 28) E of Landhuis Sta. Catarina, 29) SSeru Ronde Klip, 30) W Seru Ronde Klip, 31) E Seru Francisco, 32) Kueba di Noortkant, 33) N Seru den Banki,34) N Seru Spilon, 35) N Seri Mahuma, 36) N Roi Rincon, 37) N Papaya, 38) N Bahada di Daniel, 39) SW SeriMainshi, 40) W Seru Bayan, 41) N Kueba Bosa, 42) N Tafelberg (San Hironimo).

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Breeding

The year 1987 was dry (annual averagerainfall= 304 mm; i.e. 55 % of average). Egglaying started during October-December,after the onset of the rainy season (Fig. 2).Nests were documented at 9 of 25 sites withowl pairs, for an island-wide site nest-to-pair ratio of 36 %. In the eastern part of theisland (sites 19-25), where annual rainfallwas lower (222 mm; 40 % of average),

breeding was only found at one of six siteswith pairs, for a site nest-to-pair ratio of 17%, as opposed to 42 % for the remainder ofthe island (where annual rainfall was about329 mm, or 60 % of average).

In 1989 (annual average rainfall= 476mm; i.e. 87 % of average), following an un-usually wet and prolonged 1988 rainy sea-son partly due to Hurricane Joan (annualaverage rainfall= 1192 mm; i.e. 217 % ofaverage), Barn Owl nestlings were ob-served during March-May at six of eightnest sites. Back-calculation indicates that asecond incubation had started in January-February, which usually marks the end of

the rainy season and the beginning of thedry season. Consequently, in 1989 two

broods were attained at three of the eightmonitored breeding sites. Eleven nestswere documented at 15 sites with owlpairs, for a site nest-to-pair ratio of 73 %.The difference in site nest-to-pair ratios be-tween the dry 1987 period and the wet 1989period was significant, even when limitingthe comparison to sites visited during bothperiods (8/19 vs. 11/13; X2 = 5.78, df= 1, P< 0.025).

Mortalities

During 1989-2000, 15 of 19 (79 %) mor-talities documented were caused by motorvehicles. Two of these were brought inalive but with broken wings; another deadspecimen was clutching a mouse. The otherincidental finds involved one mortality dueto drowning in a concrete water basin, onedue to exposure to petroleum, and two ofunknown causes.

FIG. 2. Instances of observed Barn Owl breeding (back-calculated month of laying) and average monthlyrainfall, 1987-1990.



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Temporal, and spatial variability infood composition

Although introduced rodents were themain prey of the owls during the dry andwet years (respectively 61 % and 72 %; Fig.3), major differences in the importance ofspecific prey categories were evident (X2 =445.2, df = 5, P < 0.005). Compared to thedry 1987 period, the wet 1989 period indi-cated greater importance of the housemouse and insects, and a decrease of birdsand rats.

Three introduced rodents comprisedmore than half of all prey items recordedfor 1987, whereas six native mammalsamounted to less than 2 % (Table 1). Thenative mammalian prey were bats, espe-cially long-tongued (Glossophaga longiros-tris) and long-nosed bats (Leptonycteriscurasoae). The rare indigenous mouse, Calo-mys hummelincki (Martino, 2000), consti-tuted a minute fraction of the rodent prey.The native cottontail (Sylvilagus floridanus)and the introduced brown rat were re-corded as small and presumably juvenilespecimens.

Bird prey belonged to species common inall habitats on the island. The Bananaquit(Coereba flaveola) was the most abundant

bird prey, followed by the Rufous-Collared

Sparrow (Zonotrichia capensis) and the Com-mon Ground Dove (Columbina passerina).The main insect prey were grasshoppers

and cockroaches, while the main reptilestaken were two common lizard species.

Prey composition varied considerablyfrom site to site. Most striking was the largedifference (X2 = 187, df = 4, P < 0.005) inrelative consumption of prey (especially

birds and brown rats) between the pairsfrom sites 10 and 11, situated less than 1 kmapart (Fig. 4). In addition, at a cave alongthe north coast (Kueba di Noordkant, site32), bats amounted to 25 % of prey items (n= 40) whereas they generally constitutedless than 2 %.

Figure 5 presents the monthly percentageof introduced rodents in the diet plottedagainst monthly rainfall for the four siteswith at least five consecutive months ofdata. At Seru Sami (site 11) and Seri Ma-huma (site 35), the monthly percentage ofintroduced rodents in the diet roughly fol-lows monthly precipitation, with a lag ofabout one month (Fig. 5A,B). A significantpositive regression was established for bothsites for percentage of rodents versus pre-cipitation in the previous month (site 11: r2

= 0.81, n = 6, P = 0.014; site 35: r2 = 0.55, n= 8, P = 0.035). In contrast, in the SpaanseWater and Caracasbaai areas (two adjacent

bays along the leeward coast- sites 15 and19), there was little seasonal variation inprecipitation and percent rodent composi-tion; the latter of which was high comparedto sites 11 and 35 (Fig. 5C), notwithstandinglower rainfall.

FIG. 3. Gross taxonomic prey composition based on Barn Owl pellets for the (dry) 1987 and (wet) 1989 surveyperiods.



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DISCUSSION

Our results provide an estimate of about75 adult Barn Owls (31 pairs plus addi-tional solitary animals) for Curacao during1987-1990. During extensive vegetationmapping and bat population studiesthroughout the island during 1991-2001,

only three new Barn Owl sites were found(a cave in the northern escarpment of SeruFrancisco, a ledge on the eastern part of thenorthern escarpment of Seri Kibra Pikaand a seaboard cliff west of Seru Man-singa). The small number of additional sitesconfirms that the surveys herein reportedprovide an adequate indication of the sta-tus of the species on the island. Our popu-lation estimate is higher than that of Voous(1985), but still indicates a low island popu-lation size.

Densities of Barn Owl populations varytemporally and spatially, with low valuesdocumented for Esk, Scotland (1 pair/2909ha: Taylor, 1994), and SW New Jersey, USA(1 pair/2201 ha: Colvin, 1984) and highervalues documented for England (1 pair/333 ha: Bunn et al., 1982), SW Valencia,Spain (1 pair/278 ha: Martnez and Lopez,1999), Texas, USA (1 pair/218 ha: Otteni etal., 1972), Galapagos (1 pair/90 ha: deGroot, 1983) and semi-arid central Mali (1pair/6.7 ha: Wilson et al., 1986). Populationdensity in Curacao (1 pair/1200 ha) lies atthe low end of this spectrum, which mayreflect low food availability, a shortage ofsuitable nesting sites, high mortality, or acombination of these factors.

Barn owl breeding and roosting sitestend to be used over many generations. Thesites found in this study were almost exclu-sively restricted to specific spots along rela-tively undisturbed cliffs of the limestoneterraces which rim the island. Based on the29 sites visited during both survey periods,it appears that there may be significant site-use turnover. There have been a few obser-vations of owls using attics and other struc-tures within urban areas (Voous, 1983;second author, unpubl. data), but we re-corded a single bird using an attic for ashort period. Our findings confirm Voous(1983) statement that urbanized areas of theisland do not harbor important numbers of

roosts or nest sites.Surprisingly, none of the many aban-doned or old and inhabited plantationhomes we visited were active sites, eventhough observations by Voous (1983), Kris-tensen (1993) and C. Schmitz (pers. comm.)indicate that such sites were important. Itappears the sites are suffering too much

TABLE 1. Prey taxa from barn owl regurgitates inCuraao, June 1987-January 1988.

Total prey items 1661 (100%)

Mammalia; Rodentia 1017 (61.2%)

Calomys hummelincki (Husson) 6Mus musculus (L.) 528Rattus norvegicus (Berkenhout) 90R. rattus (L.) 371Rattus spp. (R. rattus or R. norvegicus) 22

Mammalia; Chiroptera 19 (1.2%)

Glossophaga longirostris Miller 11Leptonycteris curasoae (Sausurre) 5Natalus tumidirostris Miller 2

Myotis nigricans (Schinz) 1

Mammalia; Lagomorpha 4 (0.2%)

Sylvilagus floridanus (J. A. Allen) 4

Aves 506 (30.5%)

Coereba flaveola (L.) 168Columbidae 6Columbina passerina (L.) 79Hirundinidae 1

Mimus gilvus (Vieillot) 14Myarchus tyrannulus (Muller) 3Parulidae, esp. Dendroica petechia (L.) 46Passer domesticus (L.) 11Tiaris bicolor (L.) 49Trochilidae 4Tyrannidae 19Zonotrichia capensis (Mller) 89Unidentified 17

Reptilia 58 (3.5%)

Anolis lineatus Daudin 10Cnemidophorus murinus Werner 48

Insecta 57 (3.4%)

Acrididae (grasshoppers) 20Blattidae (cockroaches) 29Carabidae (ground beetles) 2Cerambicidae (longhorn beetles) 1Coleoptera (beetles) 2Gryllidae (crickets) 3



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FIG. 5. Percent rodent composition (mice and rats) in the diet of the Barn Owl in relation to rainfall for fourowl pairs from areas of the island with different rainfall patterns, May 1987-January 1988.

FIG. 4. Prey species composition for two Barn Owl pairs located < 1 km apart (sites 10, 11), and for which aminimum of 10 prey specimens was documented for each of several overlapping months in the 1987 surveyperiod.



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disturbance from intensified urbanization.Our results parallel those of Petit (1996) forendangered bats, which currently use atticsand abandoned buildings sparingly. Hu-man disturbance is also influencing the useof caves, which are traditional Barn Owlsites (Husson, 1960; Voous, 1983) and arerare on the island. Two caves well-knownas long-time Barn Owl sites (Kueba Bosaand Kueba di Hato; Voous, 1983), have not

been used by these birds since opened forrecreational use.

Seventeen of the 19 Barn Owl mortalitiesdocumented were related to human activi-ties, most of which involved traffic. Whilepreliminary, these findings suggest thattraffic, which is particularly heavy on Cu-racao, constitutes a high source of mortalityfor this species. Elsewhere, traffic is re-ported as a major and increasing source ofmortality to the Barn Owl (de Jong, 1983;Taylor, 1994).

The Barn Owl is an opportunistic preda-tor feeding primarily on small mammals.However, the house mouse and black rat,which are the most important prey itemson Curacao, seldom play a major role in thediet of Barn Owls in colder temperate re-gions because these prey live mostly in oraround houses and buildings which owlstend to avoid while hunting. In warmer re-gions, the black rat and house mouse formfree-living populations and often constituteimportant food species. On some islandsand in Mediterranean regions, where smallmammals are scarce, birds or even insects(Bunn et al., 1982; de Groot, 1983; Taylor,1994) may form an important part of thediet.

Below several roosts, the ground wasscattered with bones of subfossil regurgi-tate remains. Among these, jaws of Cura-cao rice rats, Oryzomys curasoae (McFarlaneand Debrot, in press) were often numerous(see also Husson, 1960). It appears that Ory-

zomys became extinct during the colonialperiod, possibly as a result of the introduc-tion of the black rat (Hooijer, 1959; Husson,1960; McFarlane and Debrot, in press). Ricerats appear to have been an important preyitem of the Barn Owl as is still the caseelsewhere with related Oryzomys species(e.g., O. palustris- Wolfe, 1982).

In this study we document variability infood composition in terms of trends withina year in relation to area-specific rainfall,overall differences between years in rela-tion to annual rainfall, as well as severalmonths of consistent differences betweenpairs occupying different sites. Food spe-cies composition at any given time is prob-ably the result of a variety of potential fac-t o r s , a m o n g w h i c h i n d i v i d u a l p r e ypreferences, territory characteristics, andprey availability. The last factor is particu-larly influenced by rainfall fluctuation.

Relationships between rainfall andbreeding in the Barn Owl have been docu-mented in California (Stewart, 1952), Mali(Wilson et al., 1986), and the Galapagos (de

Groot, 1983). Breeding success is alsoknown to depend on the availability of suit-able prey, particularly small rodents. Intropical and arid regions, several rodentspecies, including the black rat and housemouse, increase quickly in abundance inresponse to rainfall (de Groot, 1983; Dick-man et al., 1999; Lima et al., 1999). In theGalapagos, this was reflected in an in-creased percentage of juvenile rats andmice in the diet of owls (de Groot, 1983).Our findings suggest a similar relationshipfor Barn Owls in Curacao. Our 1987 surveydata further suggest that reduced breeding

activity in the eastern part of the island wasassociated with low rainfall in this area.Also, whereas human habitation generallyserves as a rich source of introduced ro-dents, the easternmost 10% of the island isuninhabited.

Acknowledgments.R . S i m il e er , A .Brando, and C. Schmitz provided field as-sistance and K. Dekker drafted our figures.Special thanks are due to Drs. J. H. Stockand J. Wattel of the Institute of TaxonomicZoology of Amsterdam for their assistance

in the realization of this project. We greatlyappreciate the valuable improvements sug-gested by Dr. W. J. Arendt and D. B. Mc-Nair, and the rainfall data obtained fromthe Meteorological Service of the Nether-lands Antilles and Aruba. OKSNA (Over-legorgaan Kulturele Samenwerking Neder-landse Antillen) provided student grants to



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support A. Brouwer and M. van MarwijkKooy.

LITERATURE CITEDBunn, D. S., A. B. Warburton and R. D. S. Wilson. 1982.

The Barn Owl. T. & A. D. Poyser, Calton, UK. 264pp.

Colvin, B. A. 1984. Barn owl foraging behavior andsecondary poisoning hazard from rodenticide useon farms. Ph.D. dissertation, Bowling Green StateUniversity. 326 pp.

de Groot, R. S. 1983. Origin, status and ecology of theowls in Galapagos. Ardea 71: 167-182.

de Jong, J. 1983. De kerkuil. Uitgeverij Kosmos bv,Utrecht. 77 pp.

Dickman, C. R., P. S. Mahon, P. Masters, and D. F.Gibson. 1999. Long-term dynamics of rodent popu-lations in arid Australia: the influence of rainfall.Wildl. Res. 26: 389-403.

Hooijer, D. A. 1959. Fossil rodents from Curacao andBonaire. Stud. Fauna Curacao 9: 1-27.

Husson, A. M. 1960. De zoogdieren van de Neder-landse Antillen. Martinus Nijhoff, Den Haag, TheNetherlands. 170 pp.

Husson, A. M. 1962. Zoologische bijdragen No 5. Hetdetermineren van schedelresten van zoogdieren in

braakballen van uilen. E. J. Brill, Leiden, The Neth-erlands. 63 pp.

Kristensen, I. 1993. Plantage Savonet - verleden entoekomst. Stinapa No. 35, Carmabi Foundation,Curacao. 73 pp.

Lima, M., P. A. Marquet and F. M. Jaksic. 1999. El Ninoevents, precipitation patterns, and rodent out-

breaks are statistically associated in semiarid Chile.Ecography 22: 213-218.

Martnez, J. A. and G. Lopez. 1999. Breeding ecologyof the Barn Owl (Tyto alba) in Valencia (SE Spain).

J. Ornithol. 140: 93-99.Martino, A. M. G. 2000. Caratterizzazione biologica di

Calomys hummelincki (Husson 1960) (Rodentia, Sig-modontinae): genetica, crescita, morphomeria edecologia. Ph.D. Dissertation, University La Sapi-enza, Rome. 213 pp.

McFarlane, D. A. and A. O. Debrot. An extinct oryzo-myine rodent from the Quaternary of Curacao,Netherlands Antilles. Car. J. Sci. (in press)

Meteorological Service (of the Netherlands Antillesand Aruba) 1982. Beknopt overzicht van het kli-maat van de Nederlandse Antillen. Meteorolo-gische Dienst, Curacao, Netherlands Antilles. 45pp.

Otteni, L. C., E. C. Bolen and C. Cottam. 1972. Preda-tor-prey relationships and reproduction of theBarn Owl in southern Texas. Wilson Bull. 84: 434-448.

Petit, S. 1996. The status of bats on Curacao. Biol.Cons. 77: 27-31.

Stewart, P. A. 1952. Dispersal, breeding behavior andlongevity of banded Barn Owls in North America.

Auk 69: 227-245.Taylor, I. 1994. Barn owls: predator-prey relationships

and conservation. Cambridge Univ. Press, Cam-bridge, UK. 304 pp.

Voous, K. H. 1957. The birds of Aruba, Curacao andBonaire. Stud. Fauna Curacao 12: 179-181.

Voous, K. H. 1983. Birds of the Netherlands Antilles.De Walburg Pers, Utrecht, The Netherlands. 327pp.

Voous, K. H. 1985. Additions to the avifauna of Aruba,Curacao and Bonaire, South Caribbean. Ornithol.Monogr. 36: 247-254.

Walpole, R. E. and R. H. Myers. 1978. Probability andstatistics for engineers and scientists, 2nd ed. Mac-millan Publ. Co., New York. 580 pp.

Wilson, R. T., M. P. Wilson and J. W. Durkin. 1986.

Breeding biology of the Barn Owl Tyto alba in cen-tral Mali. Ibis 128: 81-90.

Wolfe, J. L. 1982. Oryzomys palustris. Mamm. Species176: 1-5.


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