scavenging by owls: a global review and new … · documented being scavenged in a given report....

J. Raptor Res. 53(4):410–418� 2019 The Raptor Research Foundation, Inc.

SCAVENGING BY OWLS: A GLOBAL REVIEW AND NEWOBSERVATIONS FROM EUROPE AND NORTH AMERICA

MAXIMILIAN L. ALLEN1

Illinois Natural History Survey, University of Illinois, 1816 S. Oak Street, Champaign, IL 61820 USA

MICHAEL P. WARD

Illinois Natural History Survey, University of Illinois, 1816 S. Oak Street, Champaign, IL 61820 USAand

Department of Natural Resources and Environmental Sciences, University of Illinois, 1102 S. Goodwin, Urbana, IL61801 USA

DAMJAN JUZNIC AND MIHA KROFEL

Department of Forestry, Biotechnical Faculty, University of Ljubljana, Vecna pot 83, SI-1000 Ljubljana, Slovenia

ABSTRACT.—Scavenging is an important ecological function that increases individual fitness and transfersenergy between trophic levels. Scavenging by owls has been documented opportunistically through directobservations, camera trapping, and pellet analyses, but it is unknown how frequent or widespread thebehavior is. We documented three new scavenging events from North America and Europe, and alsoperformed a systematic literature review of the reports documenting scavenging by owls. The number of suchreports was similar in each decade from the 1970s to the 2000s, but the decade of the 2010s had more reportsthan all previous decades combined. Owls scavenged primarily on mammals (81%), followed by birds (16%)and reptiles (3%); almost half (47%) of carrion scavenged were Artiodactyla (hoofed mammals) and most ofthe species scavenged were larger than the feeding owl. Most reports documenting scavenging by owls werefrom either Europe (n¼14) or North America (n¼11), with few reports from Asia (n¼2), South America (n¼2), or Australia (n¼1), and none from Africa. The most frequent type of report was direct observations (n¼14), followed by camera trapping (n¼9) and pellet analyses (n¼6). Our review indicates that scavenging is awidespread behavior among owl species, but most observations were opportunistic, suggesting thatadditional incidents of scavenging by owls are likely unobserved. Further research is needed to establish thefrequency of scavenging by owls and the effects that scavenging may have on owl populations and scavengingcommunities.

KEY WORDS: Great Horned Owl; Bubo virginianus; Barred Owl; Strix varia; Ural Owl; Strix uralensis; camera trap;diet; owl; pellet analysis; scavenging.

CONSUMO DE CARRONA EN ESTRIGIFORMES: UNA REVISION GLOBAL Y NUEVAS OBSERVA-CIONES EN EUROPA Y AMERICA DEL NORTE

RESUMEN.—El consumo de carrona es una funcion ecologica importante que aumenta la eficacia biologicaindividual y transfiere energıa entre niveles troficos. El consumo de carrona por parte de Estrigiformes hasido documentado de modo oportunista por medio de observaciones directas, trampeo fotografico y analisisde egagropilas, pero se desconoce su frecuencia o cual es la magnitud de este comportamiento.Documentamos tres nuevos eventos de consumo de carrona por parte de Estrigiformes en America del Nortey Europa, y realizamos una revision bibliografica sistematica de los informes que documentan estecomportamiento en este orden. El numero de informes fue similar en cada decada desde los anos 1970 hastalos 2000, pero la decada del 2010 tuvo mas informes que todas las decadas anteriores combinadas. Los buhosconsumieron carrona principalmente de mamıferos (81%), seguido de aves (16%) y reptiles (3%); casi lamitad (47%) de la carrona fue de artiodactilos (mamıferos con pezuna) y la mayorıa de las especiesconsumidas como carrona fueron mas grandes que la especie de Estrigiformes que la consumio. La mayorıa

1 Email address: [email protected]

410

de los informes que documentaron el consumo de carrona por parte de este orden proceden de Europa (n¼14) y America del Norte (n¼11), con pocos informes de Asia (n¼2), America del Sur (n¼2) o Australia (n¼1), y ninguno de Africa. Estos informes consistieron en observaciones directas (n¼ 14) seguido de trampeofotografico (n¼9) y analisis de egagropilas (n¼6). Nuestra revision indica que el consumo de carrona es uncomportamiento muy difundido entre las especies de Estrigiformes, pero la mayorıa de las observacionesfueron oportunistas, sugiriendo que otros casos de consumo de carrona pasan desapercibidos. Se necesitanmas investigaciones para establecer la frecuencia de consumo de carrona por parte de Estrigiformes y losefectos que este consumo puede tener en sus poblaciones y en las comunidades de carroneros.

[Traduccion del equipo editorial]

Many species scavenge (Wilmers et al. 2003, Selvaand Fortuna 2007, Allen et al. 2015) and by doing soperform an ecological function that is important ondifferent scales, from increasing individual fitness(Walker et al. 2018) to serving an importantmechanism for the transfer of energy betweentrophic levels (Wilmers et al. 2003, Allen et al.2015). Scavenging is more widespread than previ-ously thought, having been documented in manyvertebrates, including most mammalian carnivoresand many avian species (Wilson and Wolkovich2011). Scavenging has also been recorded for manyspecies that had previously not been reported oreven considered as scavengers (e.g., Peers et al. 2018,Varland et al. 2018). Recent technological advance-ments, including the widespread use of cameratraps, have increased our ability to documentscavenging and improved our understanding ofscavenger ecology (Krofel 2011, Allen et al. 2015).

Owls are predatory birds that typically specialize inthe capture of small, mobile vertebrate prey (Allenand Taylor 2013, Mori and Bertolino 2015). Mostowl species are primarily nocturnal, making much oftheir behavior difficult to observe (Konig et al.1999). Scavenging by owls has been documentedopportunistically through direct observations (e.g.,Smith 1974, Novoa et al. 2016), camera trapping(e.g., Krofel 2011, Peers and Boutin 2017), andpellet analyses (e.g., Hiraldo et al. 1975, Milchev andSpassov 2017), but it is unknown how frequent orwidespread the behavior is. Carrion can be a richfood source (Wilmers et al. 2003, Wilson andWolkovich 2011), and it would be advantageous forowls to consume carrion either systematically oropportunistically, as other raptors do (Varland et al.2018). The difficulty of documenting scavengingbehavior in owls may lead to underreporting of thispotentially important behavior. Although the dearthof scavenging records involving owls suggests thatscavenging may simply be opportunistic, the diffi-culty and rarity of observing scavenging in owls haslimited our ability to study the behavior.

Here we document three new observations ofscavenging by different owl species, two from NorthAmerica and one from Europe. To improve ourunderstanding of the occurrence of scavengingamong owls, we also reviewed the scientific literatureto document the amount, seasonality, and geograph-ic extent of scavenging reports, and the mostcommon items scavenged.

METHODS

Study Area. We conducted our project at two studyareas, one in North America (hereafter Wisconsin)and one in Europe (hereafter Slovenia). TheWisconsin study area was located at the Universityof Wisconsin Lakeshore Nature Preserve, a 121-haarea that borders the southwestern shore of LakeMendota in Madison, Wisconsin (Mueller et al.2019). The preserve is primarily upland broadleafdeciduous forest, including oaks (Quercus spp.),hickories (Carya spp.), and ashes (Fraxiunus spp.).The preserve also includes a restored tallgrass prairieand several small wetlands. The climate consists ofcold (annual mean¼ –10.48C) and snowy winters towarm summers (annual mean¼ 20.68C), with meanannual precipitation of 873.8 mm (Mueller et al.2018).

In Slovenia, we conducted our study in Kocevskain the northern part of the Dinaric Mountain Range.The study area encompasses 48,340 ha of predom-inantly karstic terrain covered by Dinaric fir–beechforests (locally known as Omphalodo-Fagetum s.lat.) and smaller grassland patches, with fourdominant tree species: common beech (Fagussylvatica), silver fir (Abies alba), Norway spruce (Piceaabies), and sycamore maple (Acer pseudoplatanus).The elevation ranges from 200 to 1100 m above sealevel. The climate is a mix of influences from theAlps, the Mediterranean Sea, and the Pannoniabasin, and temperatures ranged from an averagemonthly maximum of 18.68C in the summer to anaverage monthly minimum of –0.88C in winter, withan average annual precipitation of 142.8 mm.

DECEMBER 2019 411SCAVENGING BY OWLS

Field Methods. In Wisconsin, we opportunisticallyplaced carcasses of road-killed animals (two com-mon raccoons [Procyon lotor], an eastern cottontail[Sylvilagus floridanus], and two Ring-necked Pheas-ants [Phasianus colchicus]) on five occasions fromNovember 2016 to February 2017. We monitoredwith a custom-built trail camera using a Canoncamera (Rebel T5, Tokyo, Japan) with two whiteflashes (Canon Speedlite 270EX II, Tokyo, Japan)and motion sensor (Trailmaster, Lenexa, KS, USA).We set the camera to record one photo each timemotion was detected, with no refractory period. Wechecked the camera batteries and downloaded thememory cards every 3–7 d.

In Slovenia, we placed camera traps on 25 road-killed European roe deer (Capreolus capreolus)carcasses in the region of Kocevska from 1 May2014 to 1 May 2015. Carcasses were placed atrandomly selected locations within the study areaand monitored with commercial camera traps withblack infrared (UOVision, UV565GD). We set thecamera to record 60 sec of video each time motionwas detected, with a 5-sec refractory period. Wechecked the camera batteries and downloaded thememory cards every 3–7 d.

Literature Review. In December 2018, we per-formed a systematic literature search to assess theoccurrence of scavenging among owls. We searchedWeb of Science in English for the terms ‘‘scaveng*’’and ‘‘carrion’’ and matched each with the searchterm ‘‘owl’’ and each genus name as listed inClements et al. (2018). We then read each entryand removed duplicates, mismatched publications,publications not from peer-reviewed journals, andreports of domesticated animals. We also augmentedour systematic review of the literature by searchingthe references of the papers that we reviewed for anyreports we may have missed. We calculated owl massas the average value for both sexes based on Dunning(2007) and prey mass as the mean reported mass(mammals: Macdonald 1984; birds: Dunning 2007),and determined owl habitat based on del Hoyo et al.(1999). In our numerical summaries, we consideredeach of the three original incidents we report in thisstudy separately, because they were essentially sepa-rate studies on two continents. For owl species andassociated information (season [winter¼October toMarch and summer ¼ April to September in thenorthern hemisphere], location, and study type) weconsidered each other report as a whole, but for thescavenged carrion species we included any speciesdocumented being scavenged in a given report. For

example, Mori et al. (2014) documented scavengingby a long-eared owl, for which we report the season,location, and study type, and also documentedscavenging on porcupines and martens, and weinclude both in our summary of scavenged carrion.

RESULTS

Observations. At 1436 H on 6 November 2016, weplaced an eastern cottontail carcass at the Wisconsin

Figure 1. Documentation of a Great Horned Owl feedingon an eastern cottontail carcass (Sylvilagus floridanus; top),a Barred Owl feeding on a northern raccoon carcass(Procyon lotor; middle), and a Ural Owl (Strix uralensis)feeding on a roe deer carcass (Capreouls capreouls; bottom).

412 VOL. 53, NO. 4ALLEN ET AL.

Table 1. Literature review of scavenging by owls, including the owl species, mass, habitat, location, type of report, andseason. We also summarize the reported scavenging event, including the observation type, carrion species, and prey mass.Observation type indicates whether the scavenging documented was definitive, probable, or possible based on whether theowl definitively ate and/or killed the food item.

OWL SPECIES

OWL

MASS

(kg)OWL

HABITATa LOCATION

REPORT

TYPEb SEASON

cOBSERVATION TYPE;

CARRION SPECIES

PREY

MASS

(kg) REFERENCEd

Barn Owl 0.52 G Scotland O S Possible; Europeanhedgehog (Erinaceuseuropaeus)

1.05 1

Barn Owl 0.52 G Scotland O W Possible; feral pigeon(Columbia livia)

,0.01 2

Barred Owl 0.72 F USA O W Possible; Great GrayOwl

1.08 3

Barred Owl 0.72 F USA CT W Definite; white-taileddeer (Odocoileusvirginianus), easterngray squirrel (Sciuruscarolinensis)

77, 0.5 4

Barred Owl 0.72 F USA CT W Definite; northernraccoon

6.5 5

Brown Fish Owl 0.66 F Asia O NR Definite; crocodile(Crocodylinae sp.)

NA (.10) 6

Eurasian Eagle-Owl 2.40 F Spain O S Definite; rabbit(Oryctolaguscuniculus)

2.25 7

Eurasian Eagle-Owl 2.40 F Spain P NR Definite; four bovid(Bovidae sp.)carcasses

NA (.100) 8

Eurasian Eagle-Owl 2.40 F Austria P NR Definite; roe deer 20 9Eurasian Eagle-Owl 2.40 F Bulgaria P S Definite; sheep/goat

(Ovis aries/Carpahircus), fallow deer(Dama dama),domestic pig (Susscrofa)

80, 66, 200 10

Eurasian Eagle-Owl 2.40 F Spain O B Definite; 14 DomesticChickens (Gallusgallus)

0.08 11

Eurasian Eagle-Owl 2.40 F Netherlands O S Definite; roe deer 20 12Great Gray Owl 1.08 F USA NR NR Definite; ungulate

killed by gray wolf(Canis lupus)

NA (.10) 13

Great Horned Owl 1.35 F USA CT NR Definite; black-taileddeer (Odocoileushemionus columbianus)

120 14

Great Horned Owl 1.35 F Brazil O S Possible; Molina’s hog-nosed skunk(Conepatus chinga)

1.75 15

Great Horned Owl 1.35 F USA CT B Definite; unidentifiedbird (Aves)

NA 16

Great Horned Owl 1.35 F Canada O W Definite; domestic cat(Felis domesticus)

5.0 17

Great Horned Owl 1.35 F USA CT W Definite; easterncottontail

1.40 5


study area in a hardwood forest with little under-

brush. At 0822 H on 8 November 2016, a Red-tailed

Hawk (Buteo jamaicensis) landed near the carcass and

started feeding. At 0833 H, a Great Horned Owl

(Bubo virginianus) landed at the carcass and raised its

wings in a threat display to displace the hawk. The

owl then fed intermittently for 4 min while the hawk

watched from nearby (Fig. 1a) before both birds flew

away. We did not record either species returning and

at 1634 H that afternoon a coyote (Canis latrans)

found the carcass and removed it from the areamonitored by the camera.

At 1755 H on 29 January 2017, we placed acommon raccoon carcass in an area with hardwoodforest and moderate underbrush at the Wisconsinstudy area. Later that day, at 1929 H, a Barred Owl(Strix varia) landed near the carcass and startedfeeding (Fig. 1b). The owl fed intermittently for 22min before leaving. A Virginia opossum (Didelphisvirginiana) visited the carcass on 31 January 2017,and we recorded it feeding alternately with a Red-

Table 1. Continued.

OWL SPECIES

OWL

MASS

(kg)OWL

HABITATa LOCATION

REPORT

TYPEb SEASON

cOBSERVATION TYPE;

CARRION SPECIES

PREY

MASS

(kg) REFERENCEd

Little Owl 0.16 HG Belgium O S Definite; Europeanhedgehog

1.05 18

Long-eared Owl 0.30 F Italy P W Definite; four crestedporcupines (Hystrixcristata), one marten(Martes sp.)

20, 1.25 19

Magellanic Horned Owl 1.17 OW Chile O S Possible; SouthernLapwing (Vanelluschilensis)

0.33 20

Northern Hawk Owl 0.32 F Canada CT W Definite; Canada lynx(Lynx canadensis)

11.5 21

Powerful Owl 1.35 F Australia P NR Possible; sheep (Ovisaries)

102.5 22

Snowy Owl 2.04 OH USA P W Definite; cormorant(Phalacrocorax sp.)

1.54 23

Snowy Owl 2.04 OH Russia O S Definite; reindeer(Rangifer tarandus)

181.5 24

Tawny Owl 0.48 W Poland O NR Definite; unidentifiedungulate (Ungulatasp.)

NA (.10) 25

Ural Owl 0.78 F Slovenia O S Probable; roe deerkilled by Eurasianlynx (Lynx lynx)

20 26

Ural Owl 0.78 F Slovenia CT W Probable; red deer(Cervus elaphus)killed by gray wolf

170 27

Ural Owl 0.78 F Slovenia CT S Definite; roe deer 20 5Western Screech-Owl 0.15 F USA CT W Definite; Virginia

opossum (Didelphisvirginiana)

3.75 28

a Forest (F), grasslands (G), habitat generalist (HG), open habitats (OH), open woodlands (OW), woodlands (W).b Direct observation (O), camera trap (CT), pellet analysis (P), not reported (NR).c Summer (S), winter (W), winter and summer (B), not reported (NR).d References: 1. Dunsire and Dunsire 1978; 2. Welch 2012; 3. Graves and Niemi 2006; 4. Kapfer et al. 2011; 5. This study; 6. Konig et al. 1999;7. Dıaz-Ruiz et al. 2010; 8. Hiraldo et al. 1975; 9. Leditznig et al. 2001; 10. Milchev and Spassov 2017; 11. Serrano 2000; 12. Wassink 2003; 13.Hebblewhite and Smith 2010; 14. Allen et al. 2015; 15. Anza and Zilio 2015; 16. Smallwood et al. 2010; 17. Smith 1974; 18. van de Velde andMannaert 1980; 19. Mori et al. 2014; 20. Novoa et al. 2016; 21. Peers and Boutin 2017; 22. Seebeck 1976; 23. Patterson 2007; 24. Plesak 1998;25. Jedrzejewska and Jedrzejewski 1998; 26. Krofel 2005; 27. Krofel 2011; 28. Allen and Taylor 2011.


tailed Hawk and a northern raccoon until weremoved the camera on 16 February 2017.

At 1820 H on 13 May 2014, we placed an adultEuropean roe deer carcass in a hunting area at a sitewith mixed forest and moderate underbrush at ourSlovenia study area. At 0305 H on 22 May 2014, aUral Owl (Strix uralensis) landed near the carcass andstarted feeding on a thigh where meat was exposed(Fig. 1c). The owl fed intermittently for 3 min beforeleaving. A brown bear (Ursus arctos) found thecarcass on 23 May 2014 and removed the carcassfrom the site.

Literature Review. We found and reviewed 30reports that documented scavenging involving 15owl species. The most common species were theEurasian Eagle-Owl (Bubo bubo; six reports) andGreat Horned Owl (five reports), followed by BarredOwl and Ural Owl (three reports each), and BarnOwl (Tyto alba) and Snowy Owl (Bubo scandiacus; tworeports each). Brown Fish-Owl (Ketupa zeylonensis),Great Gray Owl (Strix nebulosa), Little Owl (Athenenoctua), Long-eared Owl (Asio otus), MagellanicHorned Owl (Bubo magellanicus), Northern HawkOwl (Surnia ulula), Powerful Owl (Ninox strenua),

Tawny Owl (Strix aluco), and Western Screech-Owl(Megascops kennicottii) each had one report. The owlspecies that were documented scavenging tended tobe larger species, but ranged from 0.15–0.16 kg(Western Screech-Owl and Little Owl, respectively)to 2.4 kg (Eurasian Eagle-Owl; Table 1). The owlspecies also tended to be forest specialists (66%;Table 1), with one species each that were a generalist(Little Owl), grassland specialist (Barn Owl), openhabitat specialist (Snowy Owl), open woodlandspecialist (Malleganic Horned Owl), and woodlandspecialist (Tawny Owl).

The number of reports documenting scavengingby owls was relatively consistent in each decade fromthe 1970s to the 2000s, with a mean of 3.5 (range 1–5) reports per decade. The decade of the 2010s saw asubstantial increase with 16 reports, more than all ofthe previous decades combined (Fig. 2A). Among allreports, 37% documented scavenging in winter, 33%in summer, 7% in both seasons, and in 23% theseason was not reported.

Owls scavenged a wide range of carrion species.Most carrion species were mammals (81%), followedby birds (16%) and reptiles (3%). Among the ordersof animals scavenged, Artiodactyla (hoofed mam-mals) composed almost half (47%) of the reports,and Carnivora had as many reports (16%) as birds(Fig. 2B). The mass of scavenged prey ranged from,0.001 kg to .100 kg, but 79% of carrion speciesscavenged were larger than the foraging owl species.

Most reports documenting scavenging by owlswere from either Europe (n¼ 14) or North America(n¼ 11), with few reports from Asia (n¼ 2), SouthAmerica (n¼2), or Australia (n¼1), and none fromAfrica (Fig. 3). The most common types of report

Figure 2. Literature review of reports documentingscavenging by owls: (A) Number of published reports ofscavenging by owls by decade, (B) Taxa scavenged by owls.Mammals shown as black bars, birds as light gray bars, andreptiles as dark gray bars.

Figure 3. The type and location of reports documentingscavenging by owls. Columns indicate the methodology ofthe study and colors indicate the location (Europe, NorthAmerica, or other continent).


were direct observations (n ¼ 14), followed bycamera trapping (n ¼ 9) and pellet analyses (n ¼6); one report did not describe its methods (Fig. 3).Europe was the most common location of directobservation reports (62%) and reports using pelletanalyses (75%). Among reports derived from cameratrapping, 78% came from North America. Of thereports coming from beyond Europe and NorthAmerica, 80% of reports were direct observations.

DISCUSSION

We reported new records of scavenging by threedifferent owl species, which add to the growing bodyof evidence of scavenging by owls. The number ofreports of scavenging by owls from this decade aloneis more than for the previous four decades com-bined. This may be partly because of the increasinguse of camera traps; all the reports using cameratrapping to document scavenging by owls came fromthis decade. The relative scarcity of reports inprevious decades may also have been due to a lackof attention by researchers (Kapfer et al. 2011). Mostreports of owls scavenging are from North Americaand Europe, with few reports from other continents,although our literature review in English may havemissed some reports published in other languages.This is likely due to differences in research styles oreffort, rather than a difference in scavenging by owlsamong different continents. Europe was the sourceof most direct observations and pellet analyses. Mostof the camera-trapping reports are from NorthAmerica, where camera trapping is more often used(Burton et al. 2015). We encourage studies andreports of scavenging by owls from other continentsto help enhance our understanding of scavengingbehavior in this group of raptors.

Historical studies of owl diets relied on analyses ofpellets (Konig et al. 1999), and although a growingnumber of pellet analyses have documented scav-enging, there are problems with accurately assessingscavenging by owls from pellet analyses. When owlsscavenge larger prey they may not ingest bones ordiscernible amounts of hair and may instead eatprimarily soft tissue, which could reduce thelikelihood of detecting larger food items in pelletanalyses. It can also be difficult to know if an owl haskilled or scavenged its prey, especially for smallerprey (Kapfer et al. 2011, Mori et al. 2014). Theadvent of camera traps has provided anothermethod of documenting owl diet, particularly novelprey items and scavenging behavior (Kapfer et al.2011, Krofel 2011). New methods for studying diet,

such as DNA barcoding or stable isotope analyses,may be able to distinguish the frequency of largeungulate prey or other scavenged items in the diet ofowls in the future, although these methods will notdocument scavenging on small prey that are alsohunted.

Energetic gain is likely an important aspect ofscavenging by owls, and scavenging is thought tooccur when owls are energetically stressed, either inwinter when there may be lower food availability orduring the nesting season when they are providingfood for young (Allen and Taylor 2013, Mori et al.2014, Milchev and Spassov 2017). We found thatreports of scavenging did not appear to differ byseason, although most scavenging during summerwas documented at nests. Reports documented owlsscavenging on prey with masses ranging from small(,1 kg) to large (.100 kg), but many of thecarcasses were large ungulates or other prey thatwould be too large for owls to capture (79% ofcarrion items were larger than the scavenging owland another three carrion items were approximately75% of the owl’s mass). Each incidence of scaveng-ing from observations and camera traps appeared tohave occurred only once and owls apparently did notreturn to scavenge, even on large ungulate carcasseson which they could have fed repeatedly. Neverthe-less, scavenging owls were often feeding on speciesthat would not normally be available to them as preyand the total amount of food available fromscavenged items was typically more than would beprovided by their typical prey.

Although carrion is a rich food source, scavengingalso poses risks as a source of disease (Wilson andWolkovich 2011), interference competition withlarger predators (Wilmers et al. 2003, Allen et al.2015), and a potential source of mortality whenscavenging occurs along roads (Kapfer et al. 2011).Scavenging along roads could create conservationissues (e.g., Kapfer et al. 2011), as collisions withvehicles are one of the primary sources of mortalityfor some populations of owls (Boves and Belthoff2012, Bishop and Brogan 2013, Borda-de-Agua et al.2014).

Although scavenging is not generally associatedwith owls, many owls do cache small prey (EasternScreech-Owl [Megascops asio], Marti and Hogue1979; Boreal Owl [Aegolius funereous], Korpimaki1987; Ferruginous Pygmy-Owl [Glaucidium brasilia-num], Proudfoot and Beasom 1997), and it is likelynot a large behavioral shift from caching food toscavenging carrion. Although Artiodactyla carcasses


were most commonly scavenged in our study, evenlarge studies of scavenging of Artiodactyla carcassesrarely report scavenging by owls (Allen et al. 2015).Many long-term studies with numerous carcassesalso failed to document owls scavenging. This makessystematic documentation difficult. Further researchis needed to establish the frequency of scavenging byowls and the effects that scavenging may have on owlpopulations and scavenging communities.

ACKNOWLEDGMENTS

Funding for the study was generously provided by TheIllinois Natural History Survey and the Slovenian ResearchAgency (P4-0059).

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Received 12 March 2019; accepted 13 June 2019Associate Editor: Joseph B. Buchanan


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