Red-necked Grebes Podiceps Grisegena Research Articles

Population dynamics and survival of the Red-necked Grebe Podiceps grisegena: results from a long-term study in eastern Poland

Red-necked Grebe (RNG) breeding numbers have been declining in parts of Europe for more than 10 years. We have examined population trends and estimated, for the first time, survival rates of RNGs in a population in eastern Poland in order to explore the mechanisms behind the decline. We counted nesting pairs and recorded breeding success of RNGs nesting on fish ponds. Since 1996 we marked 91 adults and 79 young individually with colour rings and collected resightings of the marked birds. We estimated apparent survival with a Cormack–Jolly–Seber model and used estimates to create a Leslie matrix model for the study population. The population dropped from an estimated 69 breeding pairs in 1995 to a minimum of 12 pairs in 2010, and subsequently remained at 13–16 pairs until 2015. Average annual apparent survival was 0.16 in first-year females and 0.76 in adult females, or 0.18 and 0.79 for sexes pooled, respectively. Site fidelity was high only in adults. Matrix models based on the observed survival rates predicted the observed population decline until 2010. A stable model population was only reached when we increased first-year survival to 0.5. While winter severity had a strong influence on annual survival, low recruitment despite sufficient breeding success was the most important mechanism in this decline. Our observations suggest that natal dispersal, which was not compensated for by immigration, is likely the main proximate mechanism behind the decline.

Fish reduce habitat coupling by a waterbird: evidence from combined stable isotope and conventional dietary approaches

Aquatic consumers can function as habitat couplers by using allochthonous subsidies of prey that migrate across ecosystem boundaries. We examined the relative use of allochthonous (invertebrates—terrestrial or living on littoral vegetation; immigrating amphibians) versus autochthonous (aquatic invertebrates, fish) resources by the red-necked grebe Podiceps grisegena, a generalist predator, on fishless ponds versus ponds stocked with common carp Cyprinus carpio. We combined conventional methods of diet estimation with stable carbon and nitrogen analyses of egg yolks and putative prey of grebes. Prelaying grebes were observed to take mainly adult amphibians on fishless ponds and fish on stocked ponds. Alimentary tract analyses gave more weight to invertebrate prey, especially leaf beetles Donaciinae, apparently picked off water or emergent plants. Bayesian isotopic mixing models did not reveal predominance of a single food source but indicated that in the presence of fish grebes received relatively less energy for egg formation from amphibians and leaf beetles. Overall, our results show that grebes relied more on allochthonous resources (range of means 50–97 % of the biomass contribution estimated by different assessment methods) in the absence than in the presence of fish (8–23 %). We suggest that habitat coupling by waterbirds may be controlled by fish, which can suppress external prey subsidies, apart from being an attractive food for piscivorous birds.

Horned Grebe Podiceps auritus and Red-necked Grebe Podiceps grisegena in Sweden 2011 – results from a national survey

The breeding populations of Horned Grebe Podiceps auritus and Red-necked Grebe Podiceps grisegena were surveyed in Sweden 2011. The estimate for Horned Grebe was 2,000 pairs, an increase from about 1,200 pairs in 1996 towards the estimate of 2,200 pairs in 1972. The estimate for Red-necked Grebe was 1,300 pairs and the population size has most certainly increased in the last decades. Habitat use among the breeding birds differed between species and region. In south Sweden, both species were most commonly found in artificial water bodies, and a recent increase in the numbers of such waters may have contributed to the population increases. In north Sweden the species were mainly found in natural inland water bodies or along the Baltic coast. Similar long-term population trends were also seen in a long-term observational dataset of passage birds from Ottenby Bird Observatory in southeast Sweden. There was no obvious effect of the coldness at their wintering grounds on the amount of birds seen at Ottenby the following year, but indirect effects of winter harshness cannot be ruled out.

Vodne ptice in ujede Cerkniškega polja (južna Slovenija) v letih 2007 in 2008, s pregledom zanimivejših opazovanj do konca leta 2010 / Waterbirds and raptors of Cerknica polje (southern Slovenia) in 2007 and 2008, with an overview of interesting observations till the end of 2010

Between the end of February 2007 and mid-February in 2008, 73 systematic surveys of waterbirds and raptors were carried out during 10-day periods at Cerknica polje (Southern Slovenia). The main objectives of our research were: to ascertain the abundance and temporal dynamics of the species occurring here, to specify their status, to make a comparison with the past period of systematic data gathering in the 1991-1992 period, to present estimates of the breeding, migrating and wintering populations, as well as to make, on these bases, a nature-conservancy evaluation of the area. Other ornithological data, acquired till the end of 2010, were gathered as well. Between the beginning of May and the beginning of September 2007, the water in the area virtually ran dry (it was retained only in the channels of the streams), while the surface itself was partially or fully icebound from mid-November 2007 till the beginning of February 2008. By the end of 2010, a total of 129 waterbird and raptor species were recorded at Cerknica polje, while in the 2007-2008 period 83 were registered. Dynamics of the species occurrence with more than nine observations made in the area is presented in a greater detail in the species overview. The breeding status was held by 27 bird species, while further seven were forage guests that bred in the vicinity of the study area. Most of the species (118) had the status of passage visitor, whereas those with the status of summer visitor (34) and winter visitor (40) were fewer. Among the recorded species, 34 were accidental and 21 rare visitors. There were 16 winter and seven summer residents, while year-round residents were six. In all 10-day periods of the research period, four species were recorded: Mallard Anas plathyrhynchos, Grey Heron Ardea cinerea, Buzzard Buteo buteo and Kestrel Falco tinnunculus. In more than 90% of 10-day periods, the Great Egret Ardea alba was recorded as well. In the 2007-2008 period, two species were eudominant (Mallard 27.2%, Buzzard 10.1%), whereas another two were dominant (Garganey Anas querquedula 7.4%, Coot Fulica atra 6.4%). Most individuals were registered at the end of March and in early April (up to 1,978 ind.), whereas the greatest numbers of species (48) were recorded in mid-April. Between May and August, the numbers of individuals and species were low owing to the dried up lake. The smallest area of occurrence was occupied by the Cormorant Phalacrocorax carbo and a group of ducks of the genera Aythya, Bucephala and Mergellus. Gulls, egrets, herons, waders, harriers Circus sp. and the Red-footed Kestrel Falco vespertinus occurred in the greater part of the research area. 10 breeders fulfilled the criteria of the species of the greatest conservation importance, two of which (Ferruginous Duck Aythya nyroca and Curlew Numenius arquata) are species of global conservation concern, whereas seven are of conservation concern on a European scale. Among non-breeders, 14 waterbird species and raptors occurred in significant numbers (> 0.1% biogeographical population), five of which occurred at least occasionally with more than 1% of their biographical population. Two species (Red-necked Grebe Podiceps grisegena and Snipe Gallinago gallinago) breed in Slovenia only at Cerknica polje, while further six species have here at least 40% of their Slovenian breeding population

Sjeldne fugler i Norge i 2006 - Rapport fra Norsk sjeldenhetskomité for fugl (NSKF)

This is the 31st annual report from the Norwegian Rarities Committee (NSKF). The majority of records treated here are from 2006, but some older records are also included. The Norwegian rarities committee follow advises given by the Taxonomic Advisory Committee (TAC) of the Association of European Record and Rarities Committees (AERC) on issues concerning taxonomy and nomenclature. The systematic list of accepted records is set out in the following system: (1) The bird’s Norwegian name, (2) scientific name, (3) the numbers in brackets, e.g. (2, 30/32, 1), refers respectively to the ( i ) total number of records/total number of individuals up to and including 1974, ( ii ) total number of records/total number of individuals from 1975 (the foundation year of NSKF), except ( iii ) records/individuals in 2006, (4) any breeding, (5) year, (6) county, (7) number of individuals, age (1K = first calendar year etc.), sex (if known) and sometimes circumstances («rm» means that the bird was ringed), (8) site and municipality, (9) date, (10) * indicates if the record was complemented by positive evidence, and type of the evidence (F = photo, V = video-recorded, L = tape-recorded, DNA = DNA-analysis, D = found dead), (11) observers’ names in brackets, main observer(s) is specified first and emphasized with *, (12) roughly gives the species’ distribution and (13) comments concerning the records. Species, subspecies and hybrids new to the Norwegian list: With 245 accepted records presented in this report, 2006 was another good year for rare birds in Norway. A total of 42 accepted records from previous years complete the status of rare birds on the Norwegian list. There are five records presented that have been shelved. Also presented are 26 records that for some reason have not been accepted. All previous records of Booted Warbler Hippolais caligata ssp. and Bonelli’s Warbler Phylloscopus bonelli ssp. have been reassessed following the recent split of these two species. The two formerly accepted records of Snow Bunting Plectrophenax nivalis of the subspecies vlasowae have also been reassessed based on new knowledge on the variation within the nominate subspecies. Three new species to the Norwegian category A list are presented in this report. This brings the official Norwegian list to 477 species. Included in this list are accepted records in category A-C. The new species in 2006 were Masked Shrike Lanius nubicus (Utsira, Rogaland 2nd to 15 th October) and Blackpoll Warbler Dendroica striata (Reve, Rogaland 2nd to 12th November). In addition the first two Sykes’s Warblers Hippolais rama (Forus, Rogaland 11th September 1983 and Monstermyr, Vest-Agder 20th September 1997) were accepted during the reassessment of older records. A Red-necked Grebe Podiceps grisegena collected at Traena, Nordland 28th January 1949 has been accepted as the first Norwegian record of the holboellii subspecies. Two records of hybrid Blue-winged Teal Anas discors x Northern Shoveler A. clypeata (Aheim, More og Romsdal 7th – 9th June 2003 and Lista fyr, Vest-Agder 31 st July – 5th August 2006) have also been accepted as the national first and second records. General trends: Record numbers for Norway was recorded for the following species during 2006: Great Bittern Botaurus stellaris (eight records), Black Kite Milvus migrans (nine records), Mediterranean Gull Larus melanocephalus (ten records), Citrine Wagtail Motacilla citreola (nine records) and Lesser Grey Shrike Lanius minor (three records). Also, 2006 saw the highest number (six records of eleven birds) for Corn Bunting in recent times, including the first successful breeding since 1939. Six records involving ten birds of Arctic Redpoll Carduelis hornemanni of the nominate subspecies was also an all time high. Also published here are the 4th & 5th Egyptian Goose Alopochen aegyptiaca for Norway, 4 th American Black Duck Anas rubripes , 3rd Piedbilled Grebe Podilymbus podiceps , 2nd Little Shearwater Puffinus [assimilis] baroli , 3rd Swinhoe’s Storm-petrel Oceanodroma monorhis , 5th Collared Pratincole Glareola pratincola , 4 th American Golden Plover Pluvialis dominica , 8th & 9th Bonaparte’s Gull Larus philadelphia , 4th, 8th & 9th Yellow-legged Gull Larus michahellis , 10th & 11th Caspian Gull Larus cachinnans , 7 th Gull-billed Tern Sterna nilotica , 4th Isabelline Wheatear Oenanthe isabellina , 2nd Eastern Orphean Warbler Sylvia crassirostris and 2 nd Black-faced Bunting Emberiza spodocephala (cat. D).

TEMPORAL PATTERNS OF PARENTAL RESOURCE DISTRIBUTION IN THE RED-NECKED GREBE: EQUALIZING THE SHARE OF THE SURVIVORS

AbstractFood distribution within brood and parental aggression to chicks were studied in the asynchronously hatching red-necked grebe Podiceps grisegena throughout the whole period of parental care. When carrying young - during the first two weeks after hatching - parents did not interfere in sibling competition for food. The proportions of food received by each brood member reflected the dominance hierarchy. After this period, parents showed aggression to offspring, especially to the older chicks and the within-brood hierarchy of received food was gradually reversed. Junior chicks were also longer cared for than their older sibling. Male and female parents did not differ in the food apportionment among differentrank chicks. It is suggested that red-necked grebe parents change the within-brood investment allocation over time. In the first weeks after hatching, they allow biased food distribution and in consequence even brood reduction. Later, they intervene in resource allocation and attempt to equalize the post-fledging survival of all chicks. Parental aggression appears to be a means both for counteracting the competitive advantage of older sibs and for forcing the chicks to independence.

Food competition and niche separation between fish and the Red-necked Grebe Podiceps grisegena (Boddaert, 1783)

During the breeding season, the aquatic bird Red-necked Grebe Podiceps grisegena feeds on small aquatic animals, which are also an important food source for many fish species. Because grebes have to provide substantial amounts of invertebrates to their brood, competitive interactions with fish may be expected during the breeding season of grebes. Based on this hypothesis, the distribution of Red-necked Grebes, the abundances of macroinvertebrates, fish, and vegetation, as well as the water depth were determined in a shallow lake during two consecutive breeding seasons. The Red-necked Grebes only utilised the reed bed as breeding site, whereas the adjacent Lagoon, although potentially suitable as breeding site, was not used. Macroinvertebrate biomass was 5–10 times higher in the reed beds than in the Lagoon. The abundance of fish was low in the reed bed but considerably higher in the Lagoon. The results indicate habitat separation between breeding Red-necked Grebe and fish in Lake Takern, and that the separation is related to distribution of food resources birds and fish have in common.