The analysis of the clutch size variability in Cormorant (P. carbo sinensis) was based
 on study results in colony at the “Jeziorsko Reservoir” (central Poland) in 2004. There were used
 328 broods controlled 3-5 times in the season. Number of eggs in a single clutch ranged from
 1 to 7, although Cormorants mostly laid 3 to 5 eggs. Mean clutch size was 3.80 (SD = 1.0 0). The
 size of clutch depended on time of laying eggs and the part of colony where the nest with brood
 was localised. The clutch size was bigger for pairs that started laying eggs earlier and lower for
 birds bred in the part of colony where the number of nests and their density were low.Zadanie pt. „Digitalizacja i udostępnienie w Cyfrowym Repozytorium Uniwersytetu Łódzkiego kolekcji czasopism naukowych wydawanych przez Uniwersytet Łódzki” nr 885/P-DUN/2014  dofinansowane zostało ze środków MNiSW w ramach działalności upowszechniającej naukę

Janiszewski, Tomasz

Kaczmarek, Krzysztof

Kleszcz, Anna

Minias, Piotr

Rakowski, Maciej

Folia Biologica et Oecologica

English

Repozytorium Uniwersytetu Łódzkiego (University of Lodz Repository)

æ@Ga od го 0 w© \? © B G a G B © 0 ® й s B ® dû © B ©---------------- 2008 ----------------  Folia Biologica et Oecologica 4: 167-176(Acta Univ. Lodz., Folia Biol. et Oecol.)P i o t r  M i n i a s ', K r z y s z t o f  Ka c z m a r e k 2, A n n a  K l e s z c z 1, M a c i e j  Ra k o w s k i ' & T o m a s z  Ja n i s z e w s k i 31 S tu d en ts’ O rnith olog ica l Sec tion, U niversity  o f  Łódź , 1/3 B anach a S tr., 9 0 -2 3 7  Ł ód ź, Poland2 M edica l U n iversity  o f  Łód ź, 4 K ościuszki S tr ., Łódź , Poland3 D epar tm en t o f  T each er T ra in ing  and B iodiversity  S tudies, U niv ersity  o f  Łódź , 1/3 B anacha  S tr., 9 0 - 2 3 7  ŁódźVARIABILITY OF CLUTCH SIZE IN CORMORANT  (.PH ALACROCORAX CARBO SIN EN SIS ) AT THE JEZIORSKO RESERVOIR (CENTRAL POLAND) IN 2004A bstract: The analysis o f the clutch size variability in Cormorant (P. carbo sinensis) was based on study results in colony at the “Jeziorsko Reservoir” (central Poland) in 2004. There were used 328 broods controlled 3-5  times in the season. Number of eggs in a single clutch ranged from 1 to 7, although Cormorants mostly laid 3 to 5 eggs. Mean clutch size was 3.80 (SD =1.00). The size of clutch depended on time of laying eggs and the part o f colony where the nest with brood was localised. The clutch size was bigger for pairs that started laying eggs earlier and lower for birds bred in the part of colony where the number of nests and their density were low.Key w ords: clutch size, Cormorant, central Poland1. IN TR OD U CT IONClutch size is one of the primary parameters studied in bird breeding ecology. Studies focused on its variability and factors shaping this variability are numerous and multi-dimensional (e.g. La c k  1954; Pe r r i n s  1965; Pr i c e , L i o u  1989 and many others).Recently, there is a constant increase in interest shown in the issues concerning Cormorant (Phalacrocorax carbo), a species which considerably interfere with human’s fishing industry (e.g. v a n  Ee r d e n  et al. 1995; Ca r s s  et al. 2003). With regard to this matter, researches allowing to objectively estimate the influence exerted by this rapidly expanding species on the ecosys-tern, seem to be particularly vital. However, if intended to be reliable, such investigations have to reveal sufficient complexity and include several aspects of Cormorant’s population ecology. Study of elementary breeding parameters is of utmost importance among them.During the last 50 years, the size o f  Cormorant’s breeding population, its trends and dynam ics w ere subjected to a thorough exam ination (e .g. L in d e l l  et al. 1995; M e ll in  et al. 1997; PRZYBYSZ 1997; PRZYBYSZ et al. 1997; M e ll in ,  M ir o w sk a -Ib r o n  2003). D espite the postulate o f  performing such  detailed investigations also in Poland (STEMPNIEWICZ et al. 1998), data con -cerning breeding parameters o f  Cormorant is still not abundant. This shortage  o f  information is straightly con nected with frequent in accessibility  o f  nests, w hich in case o f  Cormorant su bspecies P. carbo sinensis breeding in Poland, are usually located high in the tree crow ns. In con sequ en ce, obtaining any exten sive data about clutch size presents a special difficulty. In Poland, such  broad material w as collected  only in one maritime colo n y in Kąty Rybackie  at the G ulf o f  Gdańsk (KOPCIEWICZ et al. 2003). The occurrence o f  Cormorant breeding colo ny  in the m iddle part o f  the country is a relatively recent phenom enon. Its breeding attempts in this region were observed only since the 80s o f  X X  century (J a n isz e w sk i et al. 1991; T o m ia ło jć ,  S ta w a r c z y k  2003). N everth eless, the majority o f  recorded colo nies occurred to be impermanent. The only big and stable colony is located at the Jeziorsko reservoir (JANISZEWSKI et al. 1998; OSIŃSKA, JANISZEWSKI 2006). The aim o f this paper is to describe variation o f clutch size in Cormorant (P. carbo sinensis), breeding in this colon y in 2004.2. M A TE R IA L S AND M ET HODSResearch was conducted in the colony of Cormorant, located in the ‘Jeziorsko Reservoir’ natural reserve, which forms the southern part of water body of the same name. Jeziorsko reservoir was constructed on the river Warta at the border between provinces of Łódź and Poznań (Fig. 1). Official exploitation of the reservoir started in the autumn of 1986. Water surface area equals 42 km2 during the maximum water level, whereas during minimum level it does not exceed 18 km2. Reservoir is 16,5 km long and 1.8-3.5 km wide (O r ł o w s k i  1994),“Jeziorsko Reservoir” natural reserve is not only an important breeding area for plenty of bird species, but it is also exploited by seasonal migrants asa  suitable foraging and stop-over site ( J a n i s z e w s k i  et al. 1998; O s i ń s k a , J a n i s z e w s k i  2006). Cormorant’s colony at the reservoir was first recorded in1991. In 2004, the colony was set in the proximity of Mikolajewice village (51°73’N 18°63’E), next to the former Warta riverbed. It was located in the willow thicket, mainly consisting of White Willow (Salix alba) and Grey Willow (Salix cinerea). Willows in the colony were predominantly of the shrub-type, only the minor fraction was comprised of medium high trees (up to 15 meters). The whole territory of the colony was severely sectioned by the web of channels and pools. In 2004 approximately 410 pairs of Cormorant bred in the colony.Fig. 1: Jeziorsko Reservoir with location of Cormorant (P. carbo sinensis) colony, and its structure (four distinctive parts) as GPS viewMaterial was gathered in the colony of Cormorant at the “Jeziorsko Reser-voir” natural reserve during year 2004. Colony was controlled once a week in the period between the middle of March and July. Checks of the nest content were regularly performed during every control. Dates of nest checking were precisely fixed in order to maximize accuracy of egg laying onset and clutch size estimations. Therefore, nests were checked both during the building phase, as well as later, during the incubation and offspring upbringing period. Every nest was individually marked. Nest controls were carried out either directly from a ladder or with a mirror attached to the top of 4 meter high stick. Themost inaccessible nests were observed from neighbouring trees through bino-culars. Relatively low location of nests in the colony (ranging from 2 to9 meters high) permitted successful controls of almost all of them.Approximate dates of onset of breeding were estimated during a few subsequent checks. In many cases, it was possible to define exact day of laying the first egg on the basis of two consecutive controls, provided the clutch was incomplete during the first of them. If such information was lacking, the evaluation was based on the size and the level of de-velopment of nestlings, assuming the incubation period to last for ca 4 weeks (S n o w , P e r r i n s  1998). Eventually, broods were divided into three categories (Table 1):• early broods, when eggs were laid in the last decade of March (Term 1),• intermediate broods, when eggs were laid between l sl and 20th April (Term 2),• late broods, when eggs were laid after 20lh April (Term 3).T able  1: The number of broods which of 2004started in different periodsT erm s N um ber of broodsTerm 1 (Early broods) 49Term 2 (Intermediate broods) 109Term 3 (Late broods) 24T o t a l 182The colony was clearly divided into four parts. All the parts varied distin-ctively in general conditions, which thus were likely to affect breeding activities of birds in a different way. Inter-part variation was manifested in such parameters as thickness of willow shrubs, height of shrubs and trees or simply the reciprocal location. Hence, particular parts were plausibly of different attractiveness for breeding pairs, which in turn resulted in different densities of nests (Fig. 1). Four distinctive parts of the colony were marked out:1. A part with diverse height and low density of nests. Thickness of willow shrubs also low.2. A part with maximum density of nests, which were located low in the trees. Thickness of willow shrubs medium, majority of shrubs dried up.3. A part with nests frequently placed high in the tree crowns. Such loca-tion precluded some of broods from regular controls. Thickness of shrubs medium.4. A part separated by water channels from the rest of colony. Density of nests and thickness of shrubs diverse. Some of nests also not possible to be checked.Comparisons between egg numbers laid in different parts of colony and during different periods were performed on the basis of variance analysis (ANOVA 1) and Tukey test.3. RE SULT SNumber of eggs in a single clutch of Cormorants breeding at Jeziorsko reservoir in 2004 ranged from 1 to 7 (Fig. 2, Table 2). Nevertheless, on average, a clutch consisted of 3 to 5 eggs and the cases of bigger clutches were extremely rare -  only four ones recorded in 2004.Fig. 2: Clutch size distribution in 2004T able  2: The characteristics of distribution of eggs’ number per clutch in 2004N M ean SD Skewness SE  skewness328 3.80 1.00 -0 .750 0.135We found significant differences in the mean egg numbers laid in the successive terms of the breeding season (F2;i79 = 40.234, P<  0.0001). Pairs which started laying eggs earlier had bigger clutches in comparison with those which started later (Fig. 3, Table 3).Fig. 3: Number of eggs in three groups showing different times of breeding onset in 2004. Circles are means, error bars are 1.96 SETime of laying egg sT able  3: The matrix for significance values of differences between pairs o f means in Tukey test for clutch size of Cormorants that started to breed in different time in 2004. Significant values are in boldT erm  1 T erm  2 T erm  3Mean = 4.37 Mean = 3.96 Mean = 2.5Term 1 _ 0.0488 0.0000Term 2 - - 0.0000The results of analysis of mean clutch size diversity in relationship with the part of colony in which the brood took place are presented in Fig. 4 and Table 4. It was shown that clutch size is dependent on the nest location (F3.324 = 7.705, P<  0.008), since Cormorants breeding in the Parts 2 and 3 laid significantly more eggs than those from Part 1. Birds from Part 4 on average laid intermediate number of eggs, which did not differ significantly from clutch sizes recorded in the other parts.Fig. 4: Numbers of eggs recorded in the four parts of colony (see Fig. I). Circles are means, error bars are ±  1.96 SET able  4: The matrix for significance values of differences between pairs o f means in Tukey test for Cormorant clutch size in different parts o f colony in 2004. Significant values are in boldPart 1 Part 2 Part 3 Part 4Mean =  3.26 Mean = 4.08 Mean = 3.94 Mean = 3.74Part 1 _ 0.0006 0.0227 0.0973Part 2 - - 0.9418 0.0586Part 3 - - - 0.83914. DISC USSIONClutch size is one of the major factors, which determine potential reproduc-tive capability of the species. Analysis of this parameter did not reveal any significant difference between investigated colony and most of other European colonies. Similarly to other researches, clutches of 3 to 5 eggs were principally predominant at Jeziorsko reservoir, with clutches consisting of 4 eggs recorded most frequently. Such distribution of clutch sizes is known to be typical of Cormorants. Consequently, the clutches of 1-2 or 6-7 eggs were noted only sporadically ( D e b o u t  et al. 1995; van D a m , A s b i r k  1996; P r z y b y s z  1997;KopciEWicz et al. 2003). Nevertheless, the clutches of 1 or 2 eggs are exceptionally found to comprise a considerable fraction of all the broods in the colony. Such high proportion of small clutches was recorded by PAJKERT and GÓRSKI (1997) in Cormorant’s colony at Gardno Lake in the Słowiński National Park. Authors explicated this situation with the relatively young age of breeding birds and the presence of partial nest predation exerted by the Herring Gull. Due to KOPCIEWICZ et al. (2003) a clutch composed of 4 eggs appears to be of the optimal size, as it promotes maximum reproductive output of a breeding pair with regard to the minimum cost of eggs production. The authors found out that in case of bigger clutches there is a tendency for increased losses, hence the increase in number of laid eggs has strictly limited impact on the number of fledged offspring.Research in the colony at Jeziorsko reservoir showed a significant correlation between clutch size and the onset of breeding. Similar relationship was found in Kąty Rybackie at the Gulf of Gdańsk by KOPCIEWICZ et al. (2003). Due to the authors, April clutches were on average comprised of 3.5-3.8 eggs, whereas those laid during May consisted of 3.1-3.4 eggs. Furthermore, not only time dependent differences, but also internal spatial diversification in clutch size was observed in the colony at Jeziorsko reservoir. Generally, the smallest clutches were found in Part 1, while the biggest ones in Parts 2 and 3. In Part 1 the number of nests and their density were relatively low, which implies that this area was rather suboptimal for breeding. Similar diversification was observed in Kąty Rybackie, where the smallest clutches were laid in the newly established part of colony, which was formed by relatively few nests (Kop- c iE W ic z  et al. 2003). On the one hand, such differences could be explained by different quality of birds, which breed in certain parts of colony. This could be manifested for example by various age, experience or condition of individuals. Beyond a doubt, there is a competition for breeding sites taking place within colony (BlRKHEAD, FURNESS 1985). Individuals of higher status are capable of occupying optimal places for breeding, whereas birds of lower status have to accept the suboptimal ones. Moreover, intrinsic features of bird mates, such as age, are likely to exert considerable influence on clutch size (C lu t to n -B ro c k  1988). On the other hand, the differences can be caused by lower risk of predation in more densely inhabited parts of colony. Taking into consideration predator’s traces left on the shells of destroyed eggs, tree-dwelling mammals are plausibly responsible for significant fraction of losses at the incubation stage in colony at Jeziorsko reservoir. Observations suggest that these are particularly Beech Martens (Martes foina), which were repeatedly noticed in the colony and even a litter was once found in the old Cormorant’s nests. It cannot be excluded that martens are unable to successfully cope with robbing eggs in case of close presence and aggressive behavior of several adult Cor-morants.5. R E FE R E N C ESB i r k h e a d , T . R., F u r n e s s , R. W . 1985. Regulation of seabird populations. In: M. S i b l e y , R. H. S m i t h  (eds.) Behavioural ecology. Blackwell, Oxford, pp. 145-167.C a r s s , D . N., B r e g n b a l l e , T., K e l l e r , Т. M., v a n  E e r d e n , M. R. 2003. Reducing the conflict between Cormorants Phalacrocorax carbo and fisheries on a pan-European scale: REDCAFE opens for business. Vogelwelt 124, Suppl.: 299-307.CLUTroN-BROCK, T . H. (ed.). 1988. Reproductive success. The University of Chicago Press, Chicago.D eb o ut, G ., Rov N., S e l l e r s  R. M. 1995. Status and population development o f Cormorants Phalacrocorax carbo carbo breeding on the Atlantic coast of Europe. Ardea 83 (1): 47-59.v a n  D a m , C h .,  A s b i r k , S. (eds.). 19 96 . Cormorants and human interests. Rapport IKC, Wagenin- gen, 1997.v a n  E e r d e n , M . R., K o f f i j b e r g , K ., P l a t t e e u w , M . 1995. Riding on the crest o f the wave: possibilities and limitations for a thriving population of Cormorants Phalacrocorax carbo in man-dominated wetlands. Ardea 83 (1): 1-10.J a n i s z e w s k i , T .,  M a r k o w s k i , J., M i c h a l a k , P., W o j c i e c h o w s k i, Z., H e j d u k , J. 1 9 9 1. Rzadkie gatunki ptaków stwierdzone w regionie łódzkim w latach 1983-1990. Not. Om. 32 (3-4): 117-124.J a n i s z e w s k i , T ., W ł o d a r c z y k , R„ B a r g ie l , R„ G r z y b e k , J., K a l iń s k i , A., L e s n e r , B „  M ie l -c z a r e k , S. 19 9 8. Awifauna zbiornika Jeziorsko w latach 1986-1997. Not. Om. 39 (3): 121-150.L a c k , D. 1954. The natural regulation of animal numbers. Oxford University Press, London.L i n d e l l ,  L .,  M e l l in , M ., M u s i l , P ., P r z y b y s z , J .,  Z i m m e r m a n , H . 1 9 9 5 . Status and population development o f breeding Cormorants Phalacrocorax carbo sinensis  o f the central European flyway. Ardea 83 (1): 81-92.K o p c i e w i c z , P .,  S t e m p n i e w i c z , L., N i t e c k i , C., B z o m a , S . 2003. Efekty rozrodu kormorana Phalacrocorax carbo sinensis w Kątach Rybackich. Not. Orn. 44 (1): 33-41.M e l l i n , M ., M i r o w s k a - Ib r o n , I., G r o m a d z k a , J„  K r u p a , R. 1997. Recent development o f the Cormorants breeding population in north-eastern Poland. Suppl. Ric Biol. Selvaggina 26: 89-95.M e l l i n , M ., M i r o w s k a - Ib r o n , I.  2 0 0 3. Population trends of the Great Cormorants Phalacrocorax carbo sinensis in NE Poland (1993-1999). Vogelwelt 124, Suppl.: 49-52 .O r m o w s k i , W . 1 9 9 4 . Zadania gospodarcze i dane techniczne zbiornika retencyjnego Jeziorsko. Materiały z Konferencji Naukowej „Wpływ zbiornika Jeziorsko na populacje ryb rzeki W arty” , Łódź, 14-15 III 1994.O s i ń s k a , M., J a n i s z e w s k i , T . 2 0 0 6 . Awifauna lęgowa zbiornika Jeziorsko w roku 2004 -  jej zmiany i problemy ochrony. In: J. J. N o w a k o w s k i , P. T r y j a n o w s k i, P. In d y k i e w ic z  (eds.). Ornitologia polska na progu XXI stulecia -  dokonania i perspektywy. Sekcja Ornitologiczna PTZool., Katedra Ekologii i Ochrony Środowiska UWM, Olsztyn; pp. 235-252.P a j k e r t , Z . G ó r s k i , W . 19 97 . Breeding ecology of cormorants Phalacrocorax carbo  in Słowiński National Park (Northern Poland). In: M. G r o m a d z k i , J. G r o m a d z k a  (eds.). Proc. o f the Third International Conference on Cormorants in Europe, Gdańsk, Poland 13-17 April 1993. Ekol. Pol. 45: 181-184.P e r r in s ,  C. M. 1965. Population fluctuations and clutch size in the great tit Parus major, L. J. Anim. Ecol. 34: 1010-1014.P r ic e , T ., L iou , L. 19 8 9. Selection on clutch size in birds. Am. Nat. 134: 950-959.P r z y b y s z , J . 1997. Kormoran. Monografie przyrodnicze. WLKP, Świebodzin.P r z y b y s z , J. , M e l l i n , M ., M i r o w s k a - I b r o n , I., P r z y b y s z , A., G r o m a d z k a , J. 1997. Recent development o f the Cormorants Phalacrocorax carbo sinensis population in Poland. In:M. G r o m a d z k i , J. G r o m a d z k a  (eds.). Proc. of the Third International Conference on Cormorants in Europe, Gdańsk Poland 13-17 April 1993, Ekol. Pol. 45: 111-115.S n o w , D. W., P e r r i n s , C. M . 1998. The Bird of Western Palearctic: Concise Edition. Oxford University Press.S te m p n i e w ic z ,  L., G o c , M., N it e c k i , С. 1998. O potrzebie badań ekologicznych nad kormoranem Phalacrocorax carbo  w Polsce. Not. Om. 39 (1): 33-45.T o m i a ł o j ć , L., S t a w a r c z y k , T. 2003. Awifauna Polski. Rozmieszczenie, liczebność i zmiany. PTPP „Pro Natura” , Wrocław.

Variability of clutch size in Cormorant (Phalacrocorax carbo sinensis) at the Jeziorsko Reservoir (Central Poland) in 2004

The analysis of the clutch size variability in Cormorant (P. carbo sinensis) was based
 on study results in colony at the “Jeziorsko Reservoir” (central Poland) in 2004. There were used
 328 broods controlled 3-5 times in the season. Number of eggs in a single clutch ranged from
 1 to 7, although Cormorants mostly laid 3 to 5 eggs. Mean clutch size was 3.80 (SD = 1.0 0). The
 size of clutch depended on time of laying eggs and the part of colony where the nest with brood
 was localised. The clutch size was bigger for pairs that started laying eggs earlier and lower for
 birds bred in the part of colony where the number of nests and their density were low

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Variability of clutch size in Cormorant (Phalacrocorax carbo sinensis) at the Jeziorsko Reservoir (Central Poland) in 2004

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Variability of clutch size in Cormorant (Phalacrocorax carbo sinensis) at the Jeziorsko Reservoir (Central Poland) in 2004

Abstract

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Full text

Available Versions

Repozytorium Uniwersytetu Łódzkiego (University of Lodz Repository)

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