Ornis Hungarica 2015. 23(1): 32–47. DOI: 10.1515/orhu-2015-0003 Hunting efficiency of Red-footed Falcons in different habitats

Péter Palatitz1*, Szabolcs Solt1, Éva Horváth1 & László Kotymán2

Péter Palatitz, Szabolcs Solt, Éva Horváth & László Kotymán 2015. Hunting efficiency of Red-footed Falcons in different habitats. – Ornis Hungarica 23(1): 32–47.

Abstract We studied hunting success of 13 male Red-footed Falcons by radio-telemetry in the second phase of chick rearing. We coded 484 hunting events, and the success measured in cap- tured prey biomass/minute was exceedingly high in corn fields. This is mainly caused by the fact that the effec- tiveness of hunting for vertebrate prey was high on the harvested stubble fields. Moreover the observed falcons hunted for insects in these stubble field and alfalfa fields most successfully. In the studied habitat the chick feed- ing period of Red-footed Falcons coincide with the harvest of cereal fields, and the suddenly created lower vege- tation cover increases temporarily the accessibility of prey items. Till they were available and could be efficiently harvested, the falcons hunted on the fields within a 1 km radi- us from the nesting colony for the more profitable vertebrate prey. Thereafter they searched for vertebrate prey on the fields located at average 1–2.5 km distance from the colony. In the later zone falcons started to hunt insects, too, but approximately third of the captured insects (36.4%) was consumed immediately and was not delivered to the colony. Conversely larger prey was almost always (98.1%) carried directly to the nest site. Only one part of the Field Voles was observed to be eaten regularly: the brain. Finally later in the breeding season falcons were observed more and more often to hunt in the nearest fields again, this time for insects. Probably due to the deple- tion of the distant plots, the closer fields with lower investment became a competitive alternative for the birds. Our results highlight the fact that even for such characteristic short-grass specialist birds as Red-footed Falcons the prey sources offered by arable lands might be temporarily exploited with success. Hence it is very important to integrate the measures offered by agri-environment schemes into the management of this threatened species.

Keywords: radio-telemetry, habitat use, resource utilization, Falco vespertinus, agro-environmental scheme

Összefoglalás A fiókanevelési időszak második felében követéses rádiótelemetriával vizsgáltuk 13 kék vércse hím vadászati sikerét. Összesen 484 vadászatot kódoltunk le, a vadászati sikert az átlagosan 1 perc alatt zsák- mányolt biomasszában (g) mértük. A vizsgált egyedek vadászati sikere kiemelkedő volt a kalászos kultúrákban. A gerinces préda zsákmányolási hatékonysága magas volt a gabonatarlókon, de rovarokra emellett lucernatáblá- kon is sikeresen vadásztak. Ennek oka lehetett, hogy a vércsék fiókanevelése egybeesett a kalászosok betakarítá- si időszakával, amikor a növényzeti borítás megszűnése a madarak táplálékául szolgáló fajok elérhetőségét idő- szakosan megnövelte. Ameddig eredményesen kiaknázhatóak voltak, a kék vércsék a fészektelep körüli, 1 kilométernél közelebbi táplálkozó területeken nagyobb profittal megszerezhető gerinces prédát zsákmányolták. Ezt követően az átlagos távolságú (1–2,5 km közötti) táblákon keresték a gerinces zsákmányolás lehetőségét. Ha ilyen távolságba eltávo- lodtak a fészkeiktől, már rovarokat is zsákmányoltak, de ezek mintegy harmadát (36,4%) saját maguk fogyasz- tották el. Ellenben a mezei pockoknak csak az agyvelejét ették meg, a többit szinte minden esetben a fészekhez vitték (98,1%). Mivel vélhetően a távoli (>2,5 km) zónában való táplálékkeresés és vadászat költsége legfeljebb gerinces zsákmányolás esetén térül meg a madaraknak, a költés végéhez közeledve egyre gyakrabban jelentettek versenyképes alternatívát a legközelebbi területeken megfigyelt rovarvadászatok. Eredményeink felhívják a figyelmet arra, hogy még egy olyan tipikusan pusztai fajnak tartott ragadozó ma- dár, mint a kék vércse, időszakosan hatékonyan aknázhatja ki a mezőgazdasági élőhelyek kínálta forrásokat. Fon- tos ezért, hogy a faj természetvédelmi kezelésébe bevonjuk az agrár-környezetvédelem nyújtotta eszköztárat is.

Kulcsszavak: rádió-telemetria, élőhelyhasználat, forráshasználat, Falco vespertinus, agrár-környezetvédelmi tá- mogatás P. Palatitz, Sz. Solt, É. Horváth & L. Kotymán 33

1 Red-footed Falcon Conservation Working Group, MME/BirdLife Hungary, 1121 Budapest, Költő utca 21., Hungary, www.falcoproject.eu 2 Körös-Maros National Park Directorate, 5540 Szarvas, Anna liget 1., Hungary *corresponding author: [email protected]

Introduction in the diet, and even the small 5–10 mm sized arthropods are regularly caught by Red-footed Falcons (Falco vespertinus) are the Falcons. On a typical steppe grassland gregarious in all phases of their life cyc­ with short vegetation cover as the Horto- le from breeding to migration. Single bids bágy, the following species were most often and flocks can be observed throughout the preyed upon: Elaphrus riparius, Callipta- whole year regardless of the age group or mus ita­li­cus, Decticus verrucivorus, Har- sex of the bird. The composition of these palus affinis­ , Gryllotalpa gryllotalpa, Zab­ groups, the role of individuals in search- rus te­neb­rioides, Geotrupes mutator and ing for food, or the true complexity of hunt- Amara aenea (Haraszthy et al. 1994). At ing behaviour are all not yet discovered in some habitats the following vertebrate ani- this species. In other communal feeding bird mals can also be important, especially when species (Wright et al. 2003, Weimerskirch they are superabundant in gradation years: et al. 2010), information exchange (Ward & Common Spade-foot Toads (Pelobates fus- Zahavi 1973), recruiting function (Richner cus) (Horváth 1963) and some small rodent & Heeb 1996) and the joint exploitation of species, especially the Field Vole (Micro- food resources (Krebs et al. 1972) are sup- tus arvalis) (Keve & Szijj 1957, Haraszthy posed to be the most probable reasons to et al. 1994). Besides the above mentioned form groups. We have very scarce know­ species lizards (Lacerta sp.) and sometimes ledge on the time and space pattern of hunt- small passerines­ (e.g. Sylvia sp., Alauda ing of aggregated individuals, and the fac- sp.) are also captured by Red-footed Fal- tors influencing this phenomenon in most of cons (Fülöp & Szlivka 1988). the bird species. Red-footed Falcons have two distinct for- The Red-footed Falcon is considered a aging tactics: active hunting and perch hunt- generalist predator (Cramp & Simmons ing. In the former the bird catches large in- 1980). Dietary analyses are based on ob- sects in flight, or it might hover with fast servations of nestling prey provisioning wing-beats above a spot, and then swoops or the analysis of non-digested parts of down on the prey. Perch hunting is per- the prey remains. In the Carpathian Basin formed from various elevated observa- Red- footed­ Falcons feed their chicks pre- tion posts: from the ground, vegetation, py- dominantly with insects (Insecta) (Keve & lons or wires of power lines. The bird sits Szijj 1957): mainly larger representatives on these objects, and waits until a prey item of the following orders: Orthoptera, Co­ passes by near enough to launch a success- leop­­tera and Odonata.­ Falcons can practi- ful attack either with a short glide or some cally snatch any insect either from the air, powerful wing-beats. surface of vegetation­ or from the ground Red-footed Falcons prefer grassy habitats (Ha­raszthy et al. 1994, Purger 1998). There for nesting (Haraszthy et al. 1994), colonies might be as many as 30–100 insect species are often found in the near vicinity of grazed 34 ORNIS HUNGARICA 2015. 23(1) pastures (Purger 1996). The current breed- sides grasslands while the other choose ce- ing distribution of the species in Hungary real fields besides grasslands (Palatitz et al. negatively correlates with the ratio of for- 2011). est cover within a 3 km radius circle around In this work we analyse the same data- the colony (Fehérvári et al. 2009). The ar- set (Palatitz et al. 2011) and try to find the tificial nesting colonies that harbour more reasons for the individual fine-scale hunt- than two thirds of the Hungarian population ing habitat choice and describe temporal and (Palatitz et al. 2010) were assigned to areas spatial pattern of the hunting of Red-footed where larger natural or semi-natural grass- Falcons in the chick rearing phase of nesting. lands are present (Fehérvári et al. 2012). Regular breeding pairs in some places of the Hungarian extensive agricultural landscape Methods show that in some extent birds can tolerate the lack of natural grassland habitats. There The field work was carried out in the Kar- are reports from the Bachka Region/Serbia doskúti Fehértó region of the Körös-Ma- on Red-footed Falcon colonies that existed ros National Park Directorate (KMNPI) at for decades surrounded almost exclusively the Red-footed Falcon study area between with arable lands (Fülöp & Szlivka 1988). 2006–2008 (Fehérvári et al. 2008). We used Resource utilisation of the species is not the digital map with reference to individu- yet described in the scientific literature, on- al arable land plots, that enabled us to in- ly some indirect assumptions are listed. Ob- dividually recognise each plot (Kristóf et servations carried out on the Hortobágy sug- al. 2007, Palatitz 2012). This typical Great gest that Red-footed Falcons hunted in the Plain habitat, containing high percent of close vicinity of their colonies on grasslands, seminatural grassland housed three artificial catching Orthopterans, in wet year Common nestbox colonies, where in the study years Spade-foot Toads while in dry years Field 55–95 pairs of Red-footed Falcons bred Voles were carried in large quantities to the (Kotymán et al. 2015). nest (Haraszthy et al. 1994). In the litera- We captured adult birds according to the ture and species descriptions diverse natu- permit of the Nature Protection Authorities: ral and agricultural habitats are listed, where after the eggs hatched the adults were cap- Red-footed Falcons hunt successfully (Ha­ tured near the nest using decoy birds and raszthy et al. 1994, Purger 1997, Haraszthy mist nets (Bub 1991). During the study 40 1998). The studied radio-tagged individuals birds were tagged with 3.5 gr miniature ra- clearly avoided dense, closed woody vege- dio-transmitters attached to tail feathers, tation patches. These individuals most of- which were tracked from the ground with ten visited grasslands, but neither these, nor receivers. We used the radio-tracking data the also frequently visited alfalfa fields were to describe the hunting of Red-footed Fal- preferred positively compared to the availa- cons by following the tagged individuals bility of the habitat types within the home- (Palatitz et al. 2011). range. Despite low sample sizes two groups The term ‘hunt’ was used to describe the of birds could be clearly distinguished in behaviour elements in a field to find and our previous analysis: the members of the capture prey. The duration and pattern of first group visited mainly alfalfa fields be- the hunts of females were considerably dif- P. Palatitz, Sz. Solt, É. Horváth & L. Kotymán 35 ferent form that of males’ (Palatitz et al. ing the significance of vertebrate prey items 2015), probably due to the different roles (Palatitz 2012). The dependent variable of of the sexes during nesting. The majority hunting success was formed as the poten- of food provisioned to the chicks was car- tially available prey biomass per time unit ried to the nests by the males. Therefore we = (log(prey total weight [grams]/duration of only analysed the hunts of male individu- hunt [minute]). als. In order to avoid bias only those hunts To analyse the success of hunts we used were entered into the analyses, where the decision trees (Breiman et al. 1984). We entire length of the hunt was coded (from studied the effect of the following potential- entering the actual plot till leaving). Previ- ly effective grouping variables: hunting lo- ous analyses clearly indicated that the time cation (code of the arable field), individual, spent with hunting in a given study plot was nesting location, nesting type (solitary vs. dependent first of all on the applied hunting colonial), hunting strategy (=cereal or alfal- technique (active versus perch hunting). We fa (see in detail Palatitz et al. 2011), habi- assume not only the average length (time al- tat type (grassland, cereal, alfalfa, intertilled location), but also the energy gain per time crops) and Julian date. unit also varies according to the hunting Based on the distance of the hunt from the technique. Active hunting involving­ hover- nest we assigned all hunting events by clus- ing requires significant amount of muscle ter analyses into three natural categories: work. On the other hand the energy require- 1 (near) distance < 1 km; 2 (average) dis- ment of perch hunting is much lower (Mas- tance: 1–2.5 kms and finally 3 (distant) 2.5– man & Klaasen 1987, Pennycuick 2008). 5 kms (Palatitz 2012). Therefore we only analyse in this study the QGIS 1.7.3 ‘Wroclaw’ (Quantum GIS active hunts. Each data form gave informa- Development Team 2011) and R 2.13.1 tion whether the hunt was successful or un- software were used to carry up the analyses successful, or whether the observer was un- (Calenge 2006, R Development Core Team certain. If possible we also took note of the 2011). prey with the best possible taxonomic res- olution (most often we could only distin- guish vertebrate and invertebrate prey). We Results also recorded whether the prey item was consumed, or the bird left the study plot We succeeded to code altogether 484 active with the prey (Palatitz 2012). hunts in full length of 13 male Red-footed Hunting success was measured as the bio­ Falcons. When the outcome of the hunt was mass of prey gained per time unit. To esti- known, 223 proved to be successful (48.3%) mate the biomass of invertebrate and verteb­ and 239 unsuccessful (51.7%). Their distri- rate prey we used our own measurements bution by habitat type is given in Table 1. based on live (wet) weight of the prey taxa We could assign prey category and bio- from similar habitats. As the standard devia­ mass estimate to 190 hunting events. Our tion of the two main prey category (insects analysis distinguished two significantly dif- and voles) were quite large, we gave a va­ ferent (p=0.008) groups of huntings (Figure lue of 20 to vertebrate prey and a value of 1 1). While in cereal fields (n=88) the average to insect prey in order to avoid overestimat- of biomass per unit time (grams/minute) is 36 ORNIS HUNGARICA 2015. 23(1)

Habitat type Observed active hunts Total Grass Cereal Inter Alfalfa fields land stubble tilled crops The ratio of all hunts 484 41.3% 43.6% 4.3% 10.7% The ratio of successful 223 44.4% 45.3% 1.8% 8.5% hunts Success rate* 51.8% 50.0% 19.0% 39.6% * number of successful hunts/number of total hunts Table 1. The distribution of active hunts and estimated hunting success rate of Red-footed Falcons by habitat type 1. táblázat A kék vércsék aktív vadászatainak élőhely típusonként becsült sikeressége

Figure 1. Factors affecting the success (biomass (gramm)/minute) of active hunting events of Red- footed Falcons 1. ábra A kék vércsék aktív vadászatainak sikerességét (biomassza (gramm)/ perc) befolyásoló változók döntési fája P. Palatitz, Sz. Solt, É. Horváth & L. Kotymán 37

Figure 2. Factors affecting the success (biomass (grams)/minute) of active insect hunts of Red-footed Falcons 2. ábra A kék vércsék rovar zsákmánnyal végződő vadászatainak sikerességét (biomassza (gramm)/ perc) befolyásoló változók döntési fája

1 (min.: 0.125; max.: 22), in grasslands and (within 1 km) (n=58) the average of biomass in alfalfa fields this value is 0.5 (min.: 0.08; per unit time (grams/minute) is 0.75 (min.: max.: 20; n=102). 0.125; max.: 22), while in the case of hunt- The huntings performed in cereal fields can ings performed in the average distance cate­ be further grouped into two significantly dif- gory (min.: ~1 km) (n=30) this value was 4.5 ferent groups (p=0.023) depending on how (min.: 0.14; max.: 20). The reason for this far they happened from the colony (Figu­ great difference is that in the distant cereal re 1). In the case of hunts in the near group fields 2 out of 3 huntings resulted in verteb­ 38 ORNIS HUNGARICA 2015. 23(1)

Figure 3. Decision tree on the temporal and spatial pattern of successful Red-footed Falcon hunts (distance categories: 1= distance <1 km from the nest; 2=1–2.5 km from the nest; 3= more faraway than 2.5 km from the nest) 3. ábra Döntési fa a kék vércse vadászatok sikerességének tér- és időbeli függésére (távolság kategóriák: 1: < 1 km-re a fészektől, 2: 1-2,5 km-re a fészektől, 3 >2,5 km-re a fészektől) rate prey items, (n=20), while in the case of footed Falcon hunts in the different habitat hunts closer to the colony only in 17% (n=10) types not always depends on the chance to of the cases were vertebrates caught. catch the much larger vertebrate prey items. The necessary time to capture vertebrate If we analyse the successful insect hunts prey in grasslands and alfalfa fields was 3 (n=140) with decision trees, the difference minutes, while in corn fields only 2 minutes. among habitat types is significant again However the estimated success of Red-­ (p=0.007) (Figure 2). P. Palatitz, Sz. Solt, É. Horváth & L. Kotymán 39

Figure 4. Temporal and spatial pattern of the relative frequency of successful hunts of Red-footed Falcons 4. ábra A kék vércse sikeres vadászatai relatív gyakoriságának tér- és időbeli függése

In the case of insect hunts the average Dependent variable was the frequency of of biomass per unit time (grams/minute) successful hunts, independent grouping is 0.5 (min.: 0.125; max.: 2) in alfalfa and variables were: prey-type, continuous and cereal plots (N=75) regardless of distance, category distance parameters, and day of while in grasslands (n=65) the average was year (Figure 3–4). 0.4 (min.: 0.08; max.: 2). These differences The vast majority of hunts were performed practically mean that on average a success- less than 2.5 kilometres from the colony, and ful insect hunt lasts for 4 minutes in grass- what is more important, there is a significant lands, 2 minutes in alfalfa fields, while 3 difference between the spatial pattern of in- minutes in cereal fields. sect hunts and vertebrate hunts (p=0.001). We also analysed the temporal and spa- About 80% of all insect hunts (n=140) were tial pattern of successful hunting events. recorded closer than 1 km from the nest, 40 ORNIS HUNGARICA 2015. 23(1) and the remaining 20% were recorded with- catching and transporting prey all counts in 2.5 kms. The observed successful verte- when we try to calculate the net energy gain brate hunts (n=51) showed a markedly dif- of a hunt. ferent distribution: 60% were performed in The nutritional value of insects calcu- areas located near to the nest (within 1 km), lated for dry weight is 20–25 kJ/g (Bell a further 30% were closer than 2.5 kms, and 1990), while that of Field Voles varies large- the remaining 10% were performed in dis- ly with their size, but always more than 25 tant areas (more than 2.5 kms). kJ/g (Sawicka-Kapusta 1970). The nutri- The second level of the decision tree tional value of the two main prey types of shows the temporal pattern of verte- Red-footed Falcons therefore show a similar brate hunts, and two significantly differ- magnitude per unit of weight. The digesti­ ent (p=0.019) groups can be differentiated bility of the two prey type is not known, but (Figure 3). As the year advances the ratio of both of them contain quite large quantity of vertebrate hunts changes in the closer hunt- nondigestible remains that can be found in ing plots. Earlier Red-footed Falcon catch- the pellets of the falcons (mammals: bones es predominantly vertebrate prey items in and fur, while insects: chitin). the vicinity of the colony (Figure 4). The The handling time of insects is evidently observed hunts shifted to more distant loca- smaller than that of mammals, especially in tions, as the breeding season advance, and case of smaller nestlings, when parents have insects were also caught later on. In the lat- to feed each offspring carefully. However in est phase of observations the importance of the second half of the chick rearing period insects caught near the nest increased. The investigated in our study the chicks either observed change in hunting pattern was in- swallow the prey as a whole, or the female dependent from the nesting phase of the in- tears it apart for them. Hence in the case of dividual, it was determined by the calendar male Red-footed Falcons we do not have to date. take into count the handling time differen­ ces of insect and mammal prey. The transport of an insect to the nest costs Discussion less energy than that of relatively large ver- tebrate prey. Falcons are excellent flyers, A bird in the hand is worth two in the and compared to the very high cost of find- bush? ing and catching prey, the cost of the trans- port has probably much less importance Colonially breeding bird species as Red-­ (Kvist et al. 2001, Nudds & Bryant 2002). footed Falcon are mostly characterized by To sum up besides the size of the prey item central place foraging and feeding on spa- and the effectiveness of its capture (these tially aggregated food resources (Orians & parameters together form hunting success Perason 1979). In case of the falcons – that parameter of our analysis), the time invested are unable to stock the prey – this means into finding the right hunting grounds may that after every successful hunt the food be the other major component affecting the item has to be carried back to the nest. The profitability of each hunt. nutritional value of the given prey item, its digestibility, searching and handling time, P. Palatitz, Sz. Solt, É. Horváth & L. Kotymán 41

Hunting success in different habitat National Park Directorate ensured that in all types the studied habitat types nature conscious biodiversity oriented management regimes Although the estimated biomass of mam- were applied. Although there were some mals is considerably higher then, that of in- assessments in order to monitor the yearly sects, in the appropriate hunting area the change of food resources on the study area average time needed to catch them can be (Böde 2008, Juhász 2008, Szövényi 2015), even shorter. According to our observations we do not have strong evidence to assess the the active hunt for mammal prey depend- difference of food availability on the habi- ing on the habitat type takes 2–3 minutes tat types. The importance of grasslands and on average, while that of insects 2–4 minu­ alfalfa plots in conserving biodiversity is tes. With the same investment the catching widely accepted. Probably these periodical- of mammals is probably much more profita- ly stable habitats provide favourable condi- ble for Red-footed Falcons. If the energy ex- tions for the Orthoptera species and Field penditure is equal probably catching mam- Voles that form the bulk of food carried for mal prey is more profitable for Red-footed the young of Red-footed Falcons (Báldi & Falcons, than that of insects. Consequently Kisbenedek 1997, Böde 2008). However the net energy gain for a small insect car- these prey groups are prone to large popula- ried back to the nest is diminishing as the tion fluctuations and during gradation might distance from the place of catching prey appear in virtually any habitat types that to the nest increases (diminishing return is provide minimal conditions for them (De- an inverse function of distance), while for lattre et al. 1996, Michel et al. 2006). There- a larger mammal the transport cost cannot fore it is probable that they were present in fully burn up the energy gain. high quantity and density in many habitat Catching of vertebrate prey (predomi- types, when their gradation was confirmed nantly Field Voles) was fastest in cereal in our study area. Our field observations and stubble fields then in other habitat types, it the results of trapping also confirm this as- was a very important factor in the decision sumption. of choosing hunting sites, and hence largely The accessibility of prey has differed sub- affected the spatial pattern of space use. An- stantially among the habitat types. In the other indirect indicator of the importance of study area the mowing of grasslands usually mammal prey is that in Field Vole gradation starts on the 15th of June. The first mowing years the breeding success of Red-footed of alfalfa fields continuously happened from Falcons is significantly higher than in other the second half of May, while the harvest of years (Palatitz et al. 2010). cereals started in the last week of June and Moreover hunts resulted in insect catch- went on for about a month (personal obser- ing on alfalfa and cereal stubble fields vation). This meant that in the study period proved to be more successful than those car- the grasslands mowed earlier in the season ried out on grasslands. In the study period were mostly covered with growing vegeta- on our study area considerable proportion of tion. To a lesser degree where mowing was landowners applied for agri-environmental not carried out yet, or the plot was grazed subsidies (Ángyán et al. 2003), and the na- a mosaic-like various vegetation height pre- ture protection oriented management by the vailed. The alfalfa fields that were mowed 42 ORNIS HUNGARICA 2015. 23(1) earlier than grasslands showed various ve­ The phenomenon described her is not ge­tation height depending on the date of unique, Lesser Kestrels in Spain main- mowing, the general characteristics of the ly hunt at the edges of arable fields and set plot and the applied mowing technique. The aside fields, and the extensively cultiva­ harvest of corn fields was performed paral­ ted cereal fields (Bustamante 1997, Franco lel with our observation period, so dur- & Sutherland 2004, De Frutos et al. 2009). ing the studies we could find all phases of Lesser Kestrels also catch prey faster in wheat and corn fields from the not yet cut ploughed fields than in natural grasslands or plots through the stubble fields to the al- in the edges of vegetation (Rodriguez et al. ready tilled fields. Two characteristics of the 2006), and the hunting success is closely re- cereal fields were very different from grass- lated to the used agrotechnics (Ursua et al. lands and alfalfa fields: they became open 2005, Catry et al. 2011). for birds during the study period, and the Despite our results in the given period and mowed fields were covered with very short study site it would be a mistake to underesti- vegetation. According to our data all the ob- mate the importance of natural habitats. The served Red-footed Falcon hunts in cereal role of grasslands in the choice of nesting fields were performed in stubble fields, -of sites is not a mere coincidence (Fehérvári et ten on those fields that were tilled right af- al. 2009, Fehérvári et al. 2012), on the other ter harvest. Probably the agricultural activi­ hand in the period prior chick rearing, or in ties significantly improved the chance of years with different food availability (for successful hunts. The lack of vegetation co­ example when Field Vole density is lower), ver and the disturbed burrows of voles could probably their importance is relatively more contribute largely to the observed hunting significant. success of falcons for this prey type on stub- bles. Therefore low vegetation cover and Spatial and temporal patterns of hunt- hence the good detectability of vertebrate ing success prey on stubble cereal fields might have led to higher hunting success in these fields than We observed that Red-footed Falcons effec- in grasslands or alfalfa fields respectively. tively hunted for vertebrate prey at the close Our earlier experiments showed that Or- proximity of the nest sites at the early phase thopterans emigrate from mowed fields and of our studies. After a few days they started try to find cover in the adjacent edge habi­ to hunt at more faraway plots, and we could tats (Juhász 2008). Territorial small mam- only observe successful vertebrate hunts mals probably react differently to mowing. 1–2.5 kms from the nest, or even more far The earlier mowed, and then re-grown al- away. falfa fields provided mosaic-like, massive In colonially breeding birds the compe- green mass for insects (Bretagnolle et al. tition for food increases as the number of 2011). The abundance of Orthoptera species breeding birds increases (Furness & Birk- could be higher than in other habitat types. head 1984, Brown & Brown 2001, Ainley Probably this explains why Red-footed Fal- et al. 2004). Unfortunately we have no da- cons captured insects more efficiently in the ta whether the relative larger predation pres- sparsely vegetated patches and edges of al- sure near the colonies, where hunting could falfa fields. be performed with lover travelling cost, is P. Palatitz, Sz. Solt, É. Horváth & L. Kotymán 43 reducing either the availability or abun- able. Above a certain distance threshold it dance of the prey types. In Lesser Kestrels is not worth investing in searching a more a similar phenomenon was described, when profitable hunting area (Fauchald 2009). It the decrease in prey density influenced the is possible that the nearer foraging areas, fitness of the birds in a measurable fashion rich in insects, offering lower energy intake (Bonal & Aparicio 2008). but costing less in terms of travel were cho- Some prey taxa of the falcons, for exam- sen for this reason by falcons in our study. ple the small rodents that exhibit complex It is very difficult to assess at what food behaviour can adapt to the elevated pre- availability level which distance will be dation pressure (Korpimäki et al. 1996). still efficient to hunt for food to feed the Their behaviour changes: the daily activi­ offsprings (Rodriguez et al. 2006). We ob- ty decreases and night activity increases, served that there was only a single case and hence the chance of getting caught by from the 52 successful mammal hunts day-time predators, as birds of preys is les­ (1.9%), when the prey was not carried back sened. We assume that due to strong preda- to the nest. But we often observed that the tion pressure near the colony the availabili- most energy-rich part, the brain was re- ty of voles changed, and hence as the season moved and eaten frequently by the hunting advanced Red-footed Falcons were not able bird, so a headless carcass was passed on to to deplete these resources effectively. the female or chicks. From the insect hunts The shift to more far away fields to hunt (n=140) in 36.4% the observed bird con- rodents, and the appearance of insect hunt- sumed the caught insect itself, and contin- ing coincided in time. In the mid-term of our ued hunting. observations Red-footed Falcons started to From our data we can not tell, whether in hunt insects in fields nearer than 2.5 kms to vole gradation years Red-footed Falcons ac- the colonies. Then after in the third term of tively search for rodent-rich plots in their the chick feeding, insect hunts closer than 1 home range, where they can very efficiently km to the nest site were performed the most hunt? Probably in these periods insects on- frequently. ly serve as a supplementary food resource The spatial and temporal pattern of the regarding the total biomass of the chick di- successful hunts for the two main prey type et. The percentage of insects in the diet is showed an opposing trend. To hunt mam- always higher than that of mammals’, even mal prey items offering higher net energy in the periods when the later constitute the gain the birds went more and more away primary prey choice (Böde 2008). Both the from the colonies, while they were hunt- breeding success of Red-footed Falcons and ing for insects nearer and nearer as calendar the condition of chicks suggest that Field date advanced. In some aspects hotly deba­ Voles are the corner stone of hunting in gra- ted (Pyke 1984, Ydenberg et al. 1994) how- dation years (Palatitz et al. 2010). ever optimal foraging theory (Stephens & Probably it is not easy to find good Field Krebs 1986) is still often used as a theore­ Vole yielding plots, and as they become de- tical framework for studies on animal forag- pleted very fast, more and more faraway ing. It predicts that the more distant a feed- plots needs to be visited. The feeding ecolo­ ing area is, the higher net energy intake rate gy of aggregated predators long been stu­ it must offer, otherwise its use is not profit- died by ecologists. In larger colonies infor- 44 ORNIS HUNGARICA 2015. 23(1) mation from other birds could be obtained tion oriented management of agro-ecosys- on potential feeding grounds, and hence tems (Young et al. 2005, Kleijn et al. 2009). larger areas can be profitably exploited (Ra- Our results highlight the fact that even for facz & Templeton 2003). This suggests that such characteristic grassland specialist birds the home range of Red-footed Falcons nest- as Red-footed Falcons the prey sources of- ing at larger colonies was larger than that of fered by arable lands might be temporari- birds nesting in smaller colonies or breed- ly important. If we utilise this knowledge in ing solitarily (Palatitz et al. 2011). Feeding the management of habitats, it might facili- in groups is more efficient for those animal tate the harmonisation of the needs of diffe­ food sources that are either patchy, or very rent species, and it might enlarge the scope, short-lived because of depletion due to pre- spatial dimension and efficiency of habitat dation or emigration (Jacob & Brown 2000). management. At the same time competition is stronger at colonies (Brown & Brown 2001). If due to low food availability the time necessary to Acknowledgements find food increases (Fauchald 2009) birds breeding at colonies the formerly listed ad- We express our gratitude to Tibor Ist- vantages might easily turn into disadvan­ ván Fuisz for translating the text and for tages. As in Red-footed Falcons both sol- his comments on the earlier version of the itary and colonial breeding coexists in the manu­script. same habitat (Kotymán et al. 2015) for a We also thank for creating the map data- long evolutionary time, their feeding strate­ base and carrying out basic research: Dóra gies are expected to be even more refined Neidert, Dániel Kristóf, Gergely Szövényi, (Barta & Giraldeau 2001), and therefore Zoltán Soltész, Mária Kiss, Károly Erdélyi, the analyses of their feeding behaviour by Anikó Kovács-Hostyánszki, Renata Kopena mechanistic modelling (Moorcroft et al. and our diligent undergraduate students who 1999) will be even more intriguing. all contributed to this manuscript; Ágnes When applying our results for manage- Böde, Tibor Juhász, Dóra Rideg, Anett Hor- ment and protection it is worth keeping in váth, Zsaklin Széles, Bence Lázár, Imre mind, that the results were obtained in an Sándor Piross. We thank Peter Fehérvári for extremely food-rich breeding season (Field his help in the statistical analyses. Vole gradation year), at a single Red-footed­ This research was supported by LIFE Na- Falcon breeding habitat. We hope that the ture projects (LIFE05/NAT/HU/000122, zonal partition of our feeding areas will LIFE11/NAT/HU/000926), and a PhD the- form a good basis when planning more sis was written on this theme under the su- complex research projects as in Lesser Kes- pervision of Dr. Sándor Csányi at the Insti- trel (Franco & Sutherland 2004, Catry et al. tute of Wildlife Conservation, Szent István 2011) or for the planning of nature protec- University, Gödöllő, Hungary in 2012. P. Palatitz, Sz. Solt, É. Horváth & L. Kotymán 45

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