ACTA BIOLOGICA SLOVENICA LJUBLJANA 2013 Vol. 56, [t. 1: 55–63 ACTA BIOLOGICA SLOVENICA LJUBLJANA 2013 Vol. 56, [t. 1: 55–63 Nest survival of GreatTit Parus major in spatialand temporalgradient Preživetje gnezd velike sinice Parus major v prostorskem in casovnem gradientu Dejan Bordjan and Davorin Tome* National Institute of Biology, Vecna pot 111, 1000, Ljubjana, Slovenia. *correspondence: davorin.tome@nib.si Abstract:The aim of the study was to compare nest survival of Great Tit between different regions, altitudes and years to discern which has the highest influence. Temperatureisknowntobeprominentforbreedingparametersanditchangesconsistently with altitude. Our hypothesis was that altitude has greater influence on nest survival than the region and year. Breeding parameters were monitored with the use of nest- boxes over a three year period at three altitude belts in two regions. The main factor influencing nesting success was modelled using daily survival rate in the program MARK.Wegathereddatafrom104firstnestingattemptsofwhich26failed.Although nest failure increased with altitude this was significant only for one region. There was significant difference in nest failure between the regions but not between the years. Modelling showed higher support in data for regions than for altitudes and years thus rejecting the hypothesis. Some possible reasons for such results are discussed. Keywords: Great Tit, nest survival, altitude, Slovenia Izvlecek: Namen raziskave je bil primerjati preživetje gnezd velike sinice med razlicnimi regijami, nadmorskimi višinami in leti ter tako ugotoviti, kateri dejavnik ima najvecji vpliv. Temperatura ima velik vpliv na gnezditvene parametre in se spreminja konsistentno z nadmorsko višino, zato je postavljena hipoteza, da ima nadmorska višina vecji vpliv kot leto in lokacija. Gnezditveni parametri so bili z uporabo gnezdilnic spremljani v treh letih, na treh nadmorskih višinah in dveh lokacijah. Poglavitni dejavnik, ki vpliva na preživetje gnezd, je bil zmodeliran s pomocjo programa MARK. Skupaj je bilo spremljanih 104 prvih gnezd velikih sinic med katerimi jih je 26 propadlo. Ceprav je število propadlih gnezd narašcalo z nadmorsko višino,jebilotostatisticnoznacilnosamonaenilokaciji.Jepabilastatisticnoznacilna razlika v številu propadlih gnezd med obema regijama, ne pa tudi med posameznimi leti. Modeliranje je izkazalo vecjo podporo podatkov regijam kot letom in nadmorski višini in tako zavrnilo postavljeno hipotezo. V diskusiji je omenjenih nekaj možnih razlogov za dobljene rezultate . Kljucne besede: Velika sinica, preživetje gnezd, nadmorska višina, Slovenija Acta Biologica Slovenica, 56 (1), 2013 Introduction Nest survival is influenced by many factors such as breeding density (Verhulst 1995 Newton 1998),habitat(RiddingtonandGosler2008),food availability(Newton1979),predation(Wesolowski 2002), parasites (Eeva et al. 1994), weather (Bi- onda and Brambilla 2012) and competition for resources (Högstedt 1980, Prokop 2004). It may also depend on nest site (Nealetal.1993,McCleery et al. 1996, Naef-Daenzer et al. 2001, Strusis- Timmer 2009). Cavity nesting reduces, but does not exclude, threats from predators and weather (Kluijver1951).Inmoststudiesofbreedingfailure inhole-nestingspecies,predationwasfoundtobe the most important factor (McCleeryet al. 1996, Julliard et al. 1997, Naef-Daenzer et al. 2001, Wesolowski2002),whileweatherwasconsidered as less important (Kluijver 1951, Wesolowski et al. 2002, Radford and du Plessis 2003). Great Tit is one of the most studied hole- nesting bird species (Bednekoff et al. 1994, Noordwijk et al. 1995, Cresswell and McCleery 2003, Nussey et al. 2005, Tanner et al. 2008, Eeva et al. 2009). It utilizes variety of habitats, natural or manmade (Gosler and Wilson 1997). It can breed from sea level up to the tree line (Schmid et al. 1998) and from tropics to the edge of tundra (Quader 1995). In Europe Great Tit is one of the birds most associated with studies on the influence of temperature change on breeding (Slagsvold 1976, Sather et al. 2003, Visser et al. 2006,2009a,2009b).Whiletherehavebeensome studiesconsideringchangeofbreedingparameters with latitude and across several years (Kluijver 1951, Slagsvold 1976, Sasvári and Orell 1992, Sanz et al. 2000, Sather et al. 2003, Silverin et al. 2008,Visser et al.2009a)andalsoconsidering constraintstheyarefacingatthenorthernlimitof their distribution (Veistola et al. 1995, Rytkönen and Krams 2003), there were only few studies consideringchangeinbreedingparametersacross elevation. They consider breeding distribution, species richness or altitudinal range of species (Klosius2008).Afewofthemconsiderinfluence ofaltitudeonbreedingparameters(Slagsvold1976, Krementz and Handford 1984, Beldaet al. 1998, Sanz1998),whilenonereportabouttheinfluence on nest survival. Ouraimwastocomparenestsurvivalbetween Great Tits from different altitudes. To put the results into the perspective, we compared them with results of nest survival in different regions and in different years, to found out which of the three variables is more important. Since temperature is known to influence breeding parameters prominently (Nealetal.1993,Visseretal.2009b) and since it changes consistently with altitude (Begon et al. 1996) our hypothesis is that the altitude has greater influence on nest survival than does region or year. Materials and Methods Data were gathered at two sites in two differ- entregions(Fig.1)incentralandinnorth-eastern Slovenia from 2010 to 2012. The first site, Mt. Krim (45°55’N, 14°28’E), is an 1107 m high mountaincoveredwithextensiveforestdominated by Beech Fagus sylvatica, White Fir Abies alba and Norway Spruce Picea abies. Three separate altitudinal belts 300-400, 600-750 and 900-1150 ma.s.l.wereselectedatthissite.Thesecondsite, Mt.Pohorje(46°30’N,15°34’E),isa1543mhigh mountain dominated by Beech and locally by Nor- waySpruceandWhiteFir.Againthreealtitudinal belts with same altitudinal ranges were selected. Mt. Krim has in general about 30% more rain thanMt.Pohorjeandsimilartemperature(Tab.1). Bedrock on Mt. Krim is consisted mainly from limestoneandonMt.Pohorjemainlyfromsilicate rocks (Perko and Orožen Adamic 1998). Great Tit breedingdata were collected using 112nest-boxeswithdimensions23x15x16cmand withanentrance-holeof32mm.Nest-boxesmade from wood-concrete material were placed in a line more than 50 m apart. On Mt. Krim 48 nest- boxes (16 at each altitudinal belt) were installed in 2009 and additional 16 (8 on each of the upper two altitudinal belts) in 2010. In 2010 48 (16 at each altitudinal belt) nest-boxes were installed on Mt. Pohorje. Nest-boxes were checked about once a week from mid-March to the end of June regardless whether they were empty, occupied or desertedinpreviousinspection.Duringeachvisit, occupancy of the nest-boxes was noted and the number of eggs / nestlings counted. To minimize theimpactofhumaninspectionsnest-boxeswere Bordjan, Tome: Great Tit nest survival Figure 1: Location of study sites in Slovenia. Slika 1: Lokaciji obeh raziskovanih obmocij v Sloveniji checked quickly on dry, warm days only (Kania 1989, Keller and van Noordwijk 1994). Only the firstnestingattempts inanyyearwereusedinthe analysis of sources of variation in nest survival. We regarded as failed all nests where at least one egg was laid, but breeding did not end with any successfully fledged chicks. DataoncumulativemonthlyrainfallforApril and May (main breeding period for Great Tits in Slovenia; unpublished data) from 2010 to 2012 was obtained from the nearest meteorological station (within radius of 10 km from the study site) operated by the Environmental Agency of theRepublicofSlovenia(forMt.Krim:Pokojišce Table 1: The average amount of rain and the average ambient temperatures in April and May 2010–2012 at two study regions. Tabela 1:Povprecna kolicina dežja in povprecna temperatura okolja v Aprilu in Maju obdobja 2010–2012 na dveh lokacijah. Mt. Pohorje Mt. Krim Precipitation (mm) 151 233 Temperature (oC) 11.3 11.1 and Crna vas; for Mt. Pohorje: Maribor-Tezno). Temperatures were measured using temperature loggers (LogTag Trix-8 Temperature recorder, ac- curacy±0.5°C)onbothstudysitesonallaltitudinal belts.Fromfourdailymeasurements(atnoonand then every six hours) average temperature was calculated for both regions. The program MARK was used to model the dailysurvivalrateandtoestimatetruenestsurvival (equivalentfornestsuccess)oftheGreatTitnests (White and Burnham 1999, Rotella et al. 2004). The program is sensitive to date of nest failure – nests failed at the beginning of the breeding cycle reducenestsurvivalratemorethannestsfailedat the end of breeding cycle although none of them producedoffspringattheend.Duetoweeklynest inspections, nest failure was established with an accuracy of 7 days. Seven models (all possible additivecombinations)werecarriedoutfromthree sources of variance: 1) Region (R), 2) Altitude (A) and 3) Year (Y). Akaike weights (wi) were used to select the model with the best support in the data, to find out which of the three variables influence nest failure more. Acta Biologica Slovenica, 56 (1), 2013 Chi square test was used for comparison of proportionoffailednestsamongaltitudes,regions and years. Results Altogether104firstnestingattemptsofGreat Tits were monitored, of which 26 failed (25%). Amongyears,regionsandaltitudesthepercentage of failed nests was highest in 2010, on Mt. Krim and on upper belt (Tab. 2), but the difference was significant only for regions and for altitudes on Mt. Pohorje (Chi square; Region: .21= 4.04, P< 0.05; Year Mt.Krim: .22= 3.04, P= 0.22; Year Mt.Pohorje: .22 = 3.63, P = 0.16; Altitude Mt.Krim: .22 = 2.21, P= 0.33; Altitude Mt.Pohorje: .22= 4.04, P< 0.05). Assuming constant survival for the Great Tit thedailynestsurvivalwas0.989andanestimated truenest survivalrate was 0.706. Modelwith Region( R)asasourceofvariancehadmoresupport inthedatathanmodelswithaltitude(A)andyear (Y) (Table3). Also when considering all models thatincludedanysourceofdata,regionhadagain more support (75.7%) than altitude (35.4%) and year (32.2%). Thus among the three sources of variance region seems to explain more variance in nest survival than the other two. Table 2: Percentageof failed nests on different altitudes, years and in regions, with the number of nests in parenthesis. Tabela 2:Deležpropadlihgnezdporazlicnihnadmorskihvišinah,letihinnalokacijahsprikazanimštevilomgnezd v oklepaju. Year Upper (%) Middle (%) Lower (%) Total (%) Mt. Krim 2010 2011 / 0 (1) 20 (5) 33 (9) 55 (11) 8 (12) 44 (16) 18 (22) 2012 All 2010 75 (4) 60 (5) 100 (1) 22 (9) 26 (23) 50 (2) 31 (16) 31 (39) 0 (4) 34 (29) 31 (67) 29 (7) Mt. Pohorje 2011 2012 / 0 (1) 33 (6) 0 (2) 9 (11) 0 (10) 18 (17) 0 (13) Total All 50 (2) 57 (7) 30 (10) 27 (33) 4 (25) 20 (64) 14 (37) 25 (104) Table 3: The model selection for Great Tit Parus major nest survival. Models in bold with .AIC = 2 have the greatest support in data (Burnham and Anderson 2002). Tabela 3:Izbor modelov uspešnosti gnezd velike sinice Parus major. Poudarjenimodeli imajo .AIC = 2 in imajo najvecjo podporo v podatkih (Burnham in Anderson 2002). Model K AICc .AIC Model likelihood wi w1/wj S(.R) 2 173.6690 0.0000 1.0000 0.35294 1.00 S(.R+A) 3 175.1394 1.4704 0.4794 0.16920 2.09 S(.R+Y) 4 175.3752 1.7062 0.4261 0.15039 2.35 S(.) 1 176.3623 2.6933 0.2601 0.09180 3.84 S(.R+A+Y) 5 176.5387 2.8697 0.2381 0.08405 4.20 S(.A) 2 177.0899 3.4209 0.1808 0.06381 5.53 S(.Y) 3 177.5583 3.8893 0.1430 0.05048 6.99 S(.A+Y) 4 178.1627 4.4937 0.1057 0.03732 9.46 R = region, A =altitude, Y = year, S. = basic model Bordjan, Tome: Great Tit nest survival Discussion Weconfirmedsignificantinfluenceofaltitude on nest failure of Great Tit nest only in one of the two studied regions. While in both regions percentage of failed nests, increased with altitude, with greatest percentage just on the upper altitude (Table 2). Both indicate that altitude may influence nest successbutthismaybetrueonlylocallyoritmay be obscured by some other factors. Later is supportedbysignificantlydifferentproportionoffailed nests between regions and our modelling results. These showthat the effect of altitude waslessimportantcomparedtotheeffectofregion( Table3), thusrejectingproposedhypothesis.Overallhabitat on both regions are similar, with similar human presencefactor(PerkoandOroženAdamic1998) and ambient temperature (Table 1), but differs in number and density of some predator / competitor species (Kryštufek 1991, Mihelic et al. 2000, unpublisheddata),whichcouldinfluencedifferent predationorabandonmentrate,inbedrock(Perko andOroženAdamic1998),whichcouldinfluence reproduction through different calcium availability (Tilgar et al. 2002) and in rainfall (Table 1). Predation is the most important reason for nest failure in birds (Wesolowski et al. 2002). Althoughtherearenoknownpredatorsspecialised onGreatTitsoneitherlocality,someinfluenceof bird and mammal predator generalists could be expected over apparent competition (Holt 1977). Apparent competitors (i.e. small mammals) can fluctuate greatly between years (Kryštufek and Flajšman 2007) and can support high population of predators which can increase predation pressure on alternative prey in years of low dominant prey population (Schmidt et al. 2008, Sotenšek 2012). But if this would be the case, we would expect year models to support the data better. Rather they have the lowest support in data of all three parameters. We also argue that the storage of calcium in the bedrock is less likely the candidate for different proportion of failed nests between two regions, since other breeding parameters, such as breeding density and clutch size were virtually the same among them. Average percentage of all occupied nest-boxes on Mt. Pohorje was 31.3% and 31.7% on Mt. Krim, with average clutch size in both regions being 8.9. Rain and temperature fluctuate through the season and both can have high influence on breedingsuccessofopennesters(McDonaldetal. 2004, Fairhurst and Bechard 2005, Denac 2006, Bionda and Brambilla 2012). Although it generallyhaslowereffectonholenesters( Wesolowski et al. 2002), in the absence of predation it is still the most important external cause of nest failure (Kluijver 1951, Wesolowski et al. 2002). The cause of weather related failure is a trade-off in energy allocation between incubation / brooding and feeding in adult birds. Bad weather increases on-bout time (Keller and van Noordwijk 1994, Radford et al. 2001), but also increases energetic expenditure,whichcanalmostdoubleduringcold spells(HaftornandReinertsen1985).Preyisalso less visible or accessible in bad weather conditions, which also prolongs feeding time (Keller and van Noordwijk 1994, Pasinelli 2001, Avery and Krebs 2008). Assumption that the rainfall, compared to the temperature, is more important cause of nest failure on breeding success of the Great Tits is supported by the fact that region in our study had greater influence than altitude and that there is about 30% more rain on Mt. Krim than on Mt. Pohorje, while at the same time the differenceinaveragetemperaturebetweenregions isminimal.Soalthoughaltitudeindeedhadsome influence on survival of Great Tit nests, probably indirectlythroughtheavailabilityoffood,region canhaveevengreaterwhensiteslieinregionswith markedly different precipitation regimes. Povzetek Razmerevokoljusopovezanezgeografskimi danostmiobmocijintakodolocajorazširjenostin gnezditveneparametreptic.Privelikisinicijebilo narejenih nekaj raziskav o razlikah v gnezditvenih parametrihpogeografskiširiniinmedrazlicnimi leti, zelo malo pa je bilo narejenega na podrocju vplivanadmorskevišine. Namenraziskavejebil primerjati delež preživetja gnezd velike sinice medlokacijami,nadmorskimivišinamiinletiter ugotoviti,kateriodtehdejavnikovimavecjivpliv. Temperaturaimavelikvplivnagnezdenjeptic,zato smopostavilihipotezo,daimanadmorskavišina vecji vpliv na preživetje gnezd kot regija ali pa leto. Podatki o gnezdenju so bili s pomocjo 112 Acta Biologica Slovenica, 56 (1), 2013 gnezdilnic na treh višinskih pasovih zbrani na dveh lokacijah,KriminPohorje,medleti2010in2012. S programom MARK je bila izracunana dnevna stopnja preživetja gnezd in izdelanih sedem mod- elov(vseaditivnekombinacijeparametrovlokacija, nadmorskavišinainleto).Šestvrstpticjeskupaj zasedlo49.5%gnezdilnic.Od104prvihlegelvelike sinicejihje26propadlo.Najvecjihjepropadlov letu2010,naKrimuinnazgornjivišini,vendarje bilarazlikastatisticnoznacilnasamoprirazlikah medlokacijamiinmednadmorskimivišinamina Pohorju. Dnevno preživetje gnezd je bilo 0.989, gnezditveniuspehpa0.706.Naobehlokacijahje deležpropadlihgnezdnarašcalzvišinoznajvecjim deležemnazgornjivišini,karkaže,danadmorska višina verjetno ima vpliv na preživetje gnezd. Predpostavljamo,davplivdelujeposrednopreko razlikvtemperaturi,kisemedvišinamiznacilno razlikujejo.Podrugistranirezultatimodelakažejo, Literature dajebilvplivnadmorskevišinemanjpomembenod vplivalokacije,scimerjebilapostavljenahipoteza zavrnjena.Ocenjujemo,darazlikamedlokacijama verjetnonibilaposledicamožnihrazlikvsestavi plenilcev in kompetitiorjev, ki bi lahko vplivali na propad gnezd, niti v razliki kolicine plena, temvecvkolicinipadavin.Krimjevcasuraziskave prejel okoli 30% vec padavin kakor Pohorje. Acknowledgements We thank the Slovenian Research Agency for financing the present study. 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