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Diurnal time-activity budgets in wintering Ferruginous Pochard Aythya nyroca in Tanguar Haor, Bangladesh

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Diurnal time-activity budgets in wintering Ferruginous Pochard Aythya nyroca in Tanguar Haor, Bangladesh
  INTRODUCTION The Ferruginous Pochard  Aythya nyroca is widelydistributed in Europe,Asia and Africa,but it hasundergone declines in its populations and changes indistribution over the past few decades (Ali and Ripley1978,Perennou et al  .1994,Callaghan 1997,Lopezand Mundkur 1997,Grimmett et al  .1999,Islam 2003,Robinson and Hughes 2003a,b).The primary reasonsfor its decline are habitat degradation and loss andhunting for local consumption (Callaghan 1997,Robinson and Hughes 2003a).The species is a wintervisitor to the Indian subcontinent,where pressures onits population are particularly intense (Khan 1987,Grimmett et al  .1999,Muzaffar 2003,Islam 2003).InBangladesh,the species had undergone a steadydecline by the 1990s (Lopez and Mundkur 1997),although very large numbers have been observed since2002 (Robinson and Hughes 2003b,Muzaffar 2003).The species is considered Near Threatened (BirdLifeInternational 2004),and both European and interna-tional Species Action Plans have now been formulated(Callaghan 1997,Robinson and Hughes 2003c).The Ferruginous Pochard generally feeds on arange of aquatic and terrestrial vegetable matter as wellas aquatic invertebrates,frogs and small fish (Ali andRipley 1978,Kiss et al  .1984,Poyni 1994,Petkov1998).The species seeks refuge in reedy areas withinwetland complexes,dispersing over water bodies andpaddy fields to feed during the night (Ali and Ripley1978,Grimmett et al  .1999).Although some aspects of the species’s feeding ecology have been characterised atbreeding sites (e.g.Petkov 1998,2000,Saporetti 2000,Zogaris and Handrinos 2003),little is known aboutfeeding and time-activity budgets in the winteringgrounds.Time-activity budgets reflect of a combination of factors including individual physical condition,socialstructure and environmental conditions (Paulus 1988).The amount of time allocated to various behaviours istherefore critical in understanding a species’s ecologi-cal needs and the pressures acting upon individuals.The objective of this study was to quantify time-activity budgets in wintering Ferruginous Pochard. STUDY AREA The Haor basin is located in the north-eastern regionof Bangladesh.It contains the floodplains of theMeghna river tributaries and it is characterised bynumerous shallow water bodies known locally as beels ,which coalesce in the wet season to form larger waterbodies (Rashid 1977,NERP 1993,Geisen et al  .2000).Tanguar Haor is one of the most important wetlandareas located near the northern reaches of the Haorbasin (NERP 1993,Geisen et al  .2000).With a totalarea of 9,527 ha it is among the least disturbed of waterbodies in the area (NCSIP-1 2001a).It contains exten-sive stands of open water and emergent marshvegetation.The open water areas support Hydrillaverticillata ,plus Trapa spp.,  Nymphoides spp.and Potamogeton spp.The emergent vegetation isdominated by Persicaria chinensis and P.orientalis .Themost abundant reed vegetation consists of  Phragmiteskarka ,with other reed types occurring in scatteredaggregations.The wetland supports a diverse assem-blage of aquatic invertebrates and fish.When waterlevels fall,the Haor breaks down into as many as 40beels,exposing levees in between.This habitat is idealfor wintering waterfowl (Khan 1997,NCSIP-12001b),and large flocks start to arrive from as early asOctober (Muzaffar 2003).Annual counts of 30,000–60,000 waterbirds have resulted in the desig-nation of the area as a Ramsar site (Geisen et al  .2000),but obligations associated with this status have yet tobe fulfilled (NCSIP-1 1999,Muzaffar 2003).Waterbird counts in 2002–2003 exceeded 200,000birds (Muzaffar 2003).In this study,data wereobtained from birds in Raoua beel,one of the eightbeels within the site that are most important for water-birds (NCSIP-1 2001b).Tanguar Haor is populated byc.30,000 people (Geisen et al  .2000),and the area iscontinuously traversed by motorised boats,people andtheir livestock (Geisen et al  .2000,Muzaffar 2003). METHODS Time-activity budgets were quantified using amodified scan sample approach (Baldassarre et al  .1988).Data were collected during 44 hours of obser-vations from 14 to 20 December 2002,during goodweather conditions (sunny,with occasional light windsFORKTAIL20 (2004):25–27 Diurnal time-activity budgets in winteringFerruginous Pochard  Aythya nyroca inTanguar Haor,Bangladesh SABIR BIN MUZAFFAR  Diurnal time-activity budgets were quantified for Ferruginous Pochard  Aythya nyroca wintering in Tanguar Haor,Bangladesh.Individuals spent most time resting (60%),with less time spent feeding (17%),preening (14%) and swimming (9%).The time spentfeeding was generally lower than for other  Aythya species in winter,perhaps because Ferruginous Pochard feed preferentially at night.Human disturbance during the day may be a significant factor driving this.  Forktail 20 (2004)26 and a mean temperature of 24°C).Observations weremade using a Vitacom 20–60x60 spotting scope.Behaviour was classified into five categories:preening(including scratching and splash-bathing),feeding(including dabbling,up-ending and diving),resting(inactive with eyes open or sleeping),alert (headraised),and swimming.Groups of 5–43 individuals(totalling 231 individuals over the whole study) werescanned at 5-minute intervals over 30-minute periods.The behaviour of each individual in the group wasrecorded during each scan.A new group of birds wasselected after each 30-minute period in order tomaximise statistical independence.For analysis,datawere pooled into two-hour blocks beginning at 07h00,09h00,11h00,13h00,15h00 and 17h00 (notehowever that no observations were made after dusk at18h00). RESULTS Overall,Ferruginous Pochard spent most of the dayresting (59.9%),with significantly less time spentfeeding (16.7%),preening (14.3%),swimming (8.9%)and alert (0.3%);see Fig.1.Feeding mostly compriseddabbling and diving,rather than up-ending,althoughthis was not quantified.Most feeding was observed inthe morning prior to 11h00,when it comprised30–35% of the time-activity budget.Resting behaviorpeeked from 11h00 to 15h00,when birds were inactivefor over 80% of the time.After 17h00,birds spentabout 25% of their time preening. DISCUSSION The feeding behaviour of ducks during the non-breeding season is known to differ considerably withinand among species,depending on timing and location(Paulus 1988).Inland diving ducks of the genus  Aythya usually spend less than 30% of diurnal hours feeding(Nilsson 1970),e.g.21% for Tufted Duck  Aythya fuligula in Switzerland (Pedroli 1982),and 23% forFerruginous Pochard in Bulgaria (Petkov 2003).In thepresent study,Ferruginous Pochard spent only 17% of the time feeding.In Hungary,78% of the diet of thisspecies in winter consists of animal matter (Poyni1994).Although this has a higher calorific value thanplant material (Driver et al  .1974),implying thatindividuals might need to spend less time feeding thanherbivorous species (Paulus 1988),FerruginousPochards obtain this food at greater depths comparedto other ducks (Green 1998),requiring more timeforaging.If most food was obtained at depth whilstdiving rather than when up-ending or dabbling,theproportion of time spent feeding most productively willtherefore have been even lower than the 17% recordedduring the study (see Paulus 1988).Although hunting levels have declined (Khan 1997,Geisen et al  .2000),there was considerable humanactivity,and people living in the area move freelyaround the beels.Each day,about ten large,motorisedboats (each capable of carrying up to 100 people)travelled through areas adjacent to or within Raouabeel.In addition,small,hand-paddled or motorisedboats passed through at a rate of c.3 per hour.Whenboats approached closer than 30 m,FerruginousPochard typically abandoned the site.Boats oftenpassed through large flocks,causing them to panic anddisperse.Disturbance was also caused by collection of molluscs for feeding domestic ducks,and this activitymay affect food availablity for Ferruginous Pochard(Geisen et al. 2000).Rearing domestic ducks is acommon practice in the area,with 10,000–20,000birds in total (Geisen et al  .2000).Domestic ducksintermingle with wild birds in feeding areas,but thepresence of herders close to them often causes wildducks to leave (Muzaffar 2003).Cattle herding on theshorelines also caused wildfowl to increase vigilanceand to move away from the shallow littoral zones.Theexisting fishing practices at Tanguar Haor have beenidentified as the most important threat to its wildlifeand habitats (NCSIP-1 1999,Geisen et al  .2000,Muzaffar 2003).The level of disturbance to waterbirdsis very high since the peak fishing season coincideswith peak numbers of migratory waterbirds in the area.Although there was insufficient data to test thehypothesis,human disturbance may have reducedlevels of diurnal foraging by Ferruginous Pochard infavour of nocturnal foraging,when there is less humanactivity.Nocturnal feeding activity was not quantifiedduring this study,but large flocks were seen to returnto the beel from surrounding areas at dawn.Thespecies is known to disperse around wetlands,oftenfeeding on crops at night (Ali and Ripley 1978).In addition to the disturbance to wildfowl,localpeople collect fuelwood from the area by uprootingtrees,cutting down branches and collecting twigs(Geisen et al  .2000,Muzaffar 2003).This has resultedin the gradual destruction of swamp forests in TanguarHaor (NERP 1993,Geisen et al  .2000).Replanting of  Pongamiapinnata trees has had some benefit,butfuelwood collection continues,preventing the regener-ation of swamp forests (Muzaffar 2003).Furthermore,grazing may have a severe impact on the alreadydegraded swamp forest (NCSIP-1 1999).Management plans formulated in 1997 and 2000have not yet been implemented (Geisen and Rashid1997,Geisen 2000),but this is urgently needed.With careful selection of areas within Tanguar Haor asprotected zones (NCSIP-1 2001b,Muzaffar 2003),the SABIR BIN MUZAFFAR  Figure 1 .Time-activity budgets of Ferruginous Pochard atTanguar Haor,Bangladesh,in December 2002.  Forktail 20 (2004)27 wetland could continue to be used by local people andwildlife in a sustainable manner. ACKNOWLEDGMENTS This project was funded by the Society of Wetland Scientists,Hawaii(SWS Ramsar Support Grant Program 2001;Grant AgreementNumber SWS-2001-4).I thank Enamul Haque,Bangladesh BirdClub,for his valuable advice and support in various aspects of theproject.I am also indebted to the School of Environmental Scienceand Management (SESM),Independent University,Bangladesh(IUB) for permitting and facilitating this study,with special thanksto Prof.Haroun Er Rashid (Director,SESM) and Dihider ShahriarKabir (SESM) for constant encouragement and advice throughoutthe study.Thanks also to the numerous field assistants withoutwhom the work would not have been possible:Ahmad Fuad,RabiulHassan,Khaled Mahfuz,Rashid Mahmud,Imteaz Ibne Mostafa,Habibur Rahman,Harun Er Rashid and Md.Hamidur Rahman. REFERENCES Ali,S.and Ripley,S.D (1978) Handbook of the birds of India and Pakistan:together with those of Bangladesh,Nepal,Bhutan and Sri Lanka Vol.1.Second edition . 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Diurnal time-activity budgets in wintering Ferruginous Pochard Sabir Bin Muzaffar,School of Environmental Science and Management,Independent University Bangladesh.Present address:Department of Biology,Memorial University of Newfoundland,St.John’s,Newfoundland,A1B 3X9,Canada.Email:
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