Content uploaded by Charles J Henny
Author content
All content in this area was uploaded by Charles J Henny on Apr 09, 2015
Content may be subject to copyright.
Aerial surveys of waterfowl production in North America
... Aerial surveys of waterbirds provide a rapid method for collecting data over large spatial and long temporal scales (Henny et al. 1972;Gabor et al. 1995;Rodgers et al. 1995;Kingsford 1999). Aerial surveys have covered entire small countries (Denmark, Joensen 1968Sweden, Nilsson 1975) and large parts of continents, for example North America (3.37 million km 2 , Henny et al. 1972; Alaska 206,700 km 2 Hodges et al. 1996) and Australia (2.7 million km 2 , . ...
... Aerial surveys of waterbirds provide a rapid method for collecting data over large spatial and long temporal scales (Henny et al. 1972;Gabor et al. 1995;Rodgers et al. 1995;Kingsford 1999). Aerial surveys have covered entire small countries (Denmark, Joensen 1968Sweden, Nilsson 1975) and large parts of continents, for example North America (3.37 million km 2 , Henny et al. 1972; Alaska 206,700 km 2 Hodges et al. 1996) and Australia (2.7 million km 2 , . Use of aerial surveys has varied from estimating populations of single species estimates to multispecies investigations where data acquisition is maximised by recording abundance and composition of waterbirds throughout an entire wetland system. ...
... There are logistical difficulties ground counting large or remote wetlands (Frederick et al. 1996). Due to the greater amount of time taken to complete ground surveys relative to aerial surveys and the difficulty of accessing some areas, ground surveys are likely to be less repeatable than aerial surveys (Kingsford 1999) and less practical/efficient (Henny et al. 1972;Bowden 1973;Geldenhuys 1974;Heusmann 1990;Gabor et al. 1995;Rodgers et al. 1995). ...
... Aerial surveys of waterbirds provide a rapid and cost effective method for collecting data over large spatial and long temporal scales [16][17][18][19][20][21] . Waterbirds are counted from a low flying aircraft (<50 m), with observers identifying and estimating the numbers of each species of waterbird on a wetland. ...
Tracking long-term environmental change is important, particularly for freshwater ecosystems, often with high rates of decline. Waterbirds are key indicators of freshwater ecosystem change, with groups reflecting food availability (e.g. piscivores and fish). We store waterbird (species abundance, numbers of nests and broods) and wetland area data from aerial surveys of waterbirds across Australia, mostly at the species’ level (∼100 species) from three aerial survey programs: Eastern Australian Waterbird Survey, National Survey and Murray-Darling Basin wetlands. Across eastern Australia, we survey up to 2,000 wetlands annually (October, since 1983), along 10 survey bands (30 km wide), east to west across about one third of Australia. In 2008, we surveyed 4,858 wetlands across Australia and each year (since 2010) we survey the major wetlands in the Murray-Darling Basin. These data inform regulation of hunting seasons in Victoria and South Australia, Game bird culling in NSW, State of the Environment Reporting, environmental assessments, river and wetland management, the status of individual species and identification of high conservation sites.
... The USFWS has studied waterfowl populations throughout much of North America using strip transect aerial surveys since 1955 (7,8) and in Alaska since 1957, as well as using field studies of individual populations. Waterfowl survey information was obtained from published reports and an unpublished manuscript prepared by personnel of the USFWS. ...
... Although long-term surveys have been carried out for breeding waterfowl in mid-continent areas of North America since 1955 (Henny et al., 1972), similar surveys were not initiated in the Atlantic Flyway until several decades later. The Atlantic Flyway Breeding Waterfowl Survey (AFBWS) was initiated in 1988, underwent several refinements , and became standardized in 1993 (Heusmann and Sauer, 1997, 2000). ...
We used linear regression to analyze population trends that were collected during the Atlantic Flyway Breeding Waterfowl Survey for key waterfowl species that breed in New Jersey. The population trend for indicated breeding pairs of mallards (Anas platyrhnchos) and American black ducks (A. rubripes) declined, while the trend for wood ducks (Aix sponsa) increased. Atlantic Flyway Resident Population Canada geese (Branta canadensis) exhibited no trend. Population trends for these species at the whole Atlantic Flyway Breeding Waterfowl Survey scale were similar to those observed in New Jersey. A potentially important role of salt hay farms in the ecology of breeding black ducks in Delaware Bay marshes may have been overlooked in the past. However, since New Jersey is more important as a wintering than breeding area for black ducks, restored functionality of these marshes should benefit the black duck population as a whole.
... Észak-Amerikában a polgári célú moto- ros kisrepülőgépekről történő légi felméré- sek alkalmazása a vadbiológiában több év- tizedes múltra tekint vissza, különösképpen a vízimadarak körében ( Henny et al. 1972). A felmérési technológia fejlesztésével több irányban is történtek kezdeményezések. ...
Légifelvételek, űrfelvételek alkalmazása évtizedek óta széles körben elterjedt módszer a különböző kutatási programok támogatására. Mindazonáltal a kutatás-specifikus légifelvételek, ortofotók és élőhelytérképek megrendelése gyakran túlmutat egy adott program költségvetésén. Kiváló alternatívát (sőt esetenként egyedüli megoldást) jelentenek a rádió-irányítású légi járművekről (modellrepülőgépekről és multicopterekről) készített felvételek a természetvédelmi és biológiai kutatások számára (pl. madárfészek-számlálás, vadszámlálás, vegetációtérképezés stb.). A speciális kialakítású modellrepülőgépek segítségével a felmérések profiljának és céljának megfelelően térképezhetjük fel a vizsgálati területet, amely munkálatok sok esetben más módszerrel nem – vagy csak nagyobb zavarás mellett – végezhetők el.
[Usage of airborne images has been widely pervading in the different research programs. The high costs of the research-specific airborne imaging techniques and habitat-mapping is often beyond the budget of the programs. Airborne images, made by radio controlled (r-c) model airplanes provide a perfect alternative for the environmental and biological researches. The model airplanes give the possibility for landscape mapping or count field objects, which can not be done with any other methods (or just with bigger efforts and disturbance). For example: game counting, nest counting, survey of different microhabitat patches or vegetation mapping.]
... Our fine-scale study of relationships between habitat quality and production corroborate results from analyses at a continental scale, the results of which usually indicated declines in production with poorer habitat conditions (Crissey 1969, Henny et al. 1972, Batt et al. 1989, but see Pospahala et al. 1974). Hatching date also correlated with survival. ...
Wetland drainage has heavily impacted mallard (Anas platyrhynchos) breeding areas and decreased the amount of wetland area available to mallard broods. Also, habitat selection by mallard broods is poorly understood. Therefore, we investigated habitat use by mallard broods, monitored habitat availability, and tested for habitat selection by monitoring 29 mallard hens and their broods via radio telemetry in southwestern Manitoba, 1987-89. Habitat availability varied (P < 0.10) among years. Some broods selected habitat (P < 0.10), but there was no consistency in the types of wetlands selected (P > 0.10) by broods. Seasonal, small semipermanent, and large semipermanent wetlands were selected (P < 0.10) by 3, 2, and 7 broods, respectively; 4 broods displayed no habitat selection (P > 0.10). Broods spent 10, 5, and 85% of the first 30 days posthatching on seasonal, small semipermanent, and large semipermanent wetlands, respectively, which closely reflected wetland availability (10, 5, and 84%, respectively.) Most inter-wetland movements were made ≤1 week of hatch. Broods that hatched in areas with low wetland density moved farther (P = 0.04) from nests to the first wetlands they used than broods hatched in areas with high wetland density, implying that nests were distributed randomly with respect to distance from water. However, broods that moved farther had lower duckling survival (P = 0.08) regardless of the density of wetlands on the area they inhabited. Wetlands of all types and sizes should be preserved at the highest density possible for mallard brood habitat because each wetland type available was selected by some broods, and the distance moved by broods was directly related to wetland density and inversely related to survival.
... Indirect methods used to measure visibility bias include regression techniques (Caughley et al. 1976; Hone 1986), double survey methods (Magnusson et al. 1978; Caughley and Grice 1982; Bayliss 1986), and line transect methods (Eberhardt 1968Eberhardt , 1978 Hone, unpublished data). Aerial survey has also been applied to birds (Guiler 1957; Matthews 1960; Kadlec and Drury 1968; Martinson and Kaczynski 1969; Henny et al. 1972; Stott and Olsen 1972; Hale 1974; Blackman 1979; Prater 1979; Caughley and Grice 1982; Broome 1985; Braithwaite et al. 1986). Where bird nests are conspicuous, aerial survey is often used t o monitor their numbers as an index of breeding success (Grier 1981 on bald eagles; Brickhill 1985 on mallee fowl), and similarly for other species such as crocodilians (Chabreck 1966; Bayliss et al. 1986). ...
Aerial surveys of magpie geese, their nests, and whistling ducks (both species combined) provided density estimates that are lower than those derived from low-level aerial photography. The degree of underestimation differs markedly between species and season. The effect of density on observer counts was examined over a large range (counts of a few to tens of thousands). Observer and photgraphic counts on the same transect were paired, and the regression between the two was significantly linear for both species in each season. The main causes of consistent visibility bias were obstructive floodplain vegetation in the wet season and undercounting of flocks of all sizes (10-1000) in the dry season. -from Authors
... Indirect methods used to measure visibility bias include regression techniques (Caughley et al. 1976; Hone 1986), double survey methods (Magnusson et al. 1978; Caughley and Grice 1982; Bayliss 1986), and line transect methods (Eberhardt 1968Eberhardt , 1978 Hone, unpublished data). Aerial survey has also been applied to birds (Guiler 1957; Matthews 1960; Kadlec and Drury 1968; Martinson and Kaczynski 1969; Henny et al. 1972; Stott and Olsen 1972; Hale 1974; Blackman 1979; Prater 1979; Caughley and Grice 1982; Broome 1985; Braithwaite et al. 1986). Where bird nests are conspicuous, aerial survey is often used t o monitor their numbers as an index of breeding success (Grier 1981 on bald eagles; Brickhill 1985 on mallee fowl), and similarly for other species such as crocodilians (Chabreck 1966; Bayliss et al. 1986). ...
Most geese (95-97%) and all major breeding colonies occurred on the extensive coastal floodplains W of Arnhem Land, a region of high rainfall. Total goose numbers were relatively stable between consecutive seasons and years, varying from 1.97 × 106 to 2.97 × 106. Nest numbers were also relatively stable between years, varying from 1.67 × 105 to 2.46 × 105. However, their range expanded in the wet season as the geese dispersed across the floodplains to nest, and it contracted in the dry season as they concentrated in high densities at sources of permanent fresh water and food. Variations in distribution between years within the same season most likely reflected local variations in rainfall. Dry-season densities were highest where roosting and feeding areas occurred together (shallow fresh water and short grass lawns or extensive patches of Eleocharis spp., respectively). Wet-season densities were highest in areas that provided a broad range of nest and food plants (mainly Oryza, Hymenachne, Ischaemum and Eleocharis spp). Between the wet seasons of 1984-1985, the exotic shrub Mimosa pigra had an estimated mean rate of spread of 13.6 km yr-1, decreasing the extent of magpie goose breeding habitat and posing the most significant conservation threat to this species. -from Authors
In the last decade, the use of drones has proven to be the major innovation for studying various aspects of waterbird breeding biology, overcoming the environmental obstacles inherent in monitoring their breeding sites. The Squacco Heron (Ardeola ralloides) represents an example of the aforementioned difficulties, since it nests in impenetrable reed beds and nearby bushes, trees and shrubs. The present work reports the results of drone assessment of nest counting and reproductive success of the Squacco Heron in a colony in the Po Delta (NE Italy). At the beginning of the breeding season, far more nests (46) were found using drones than by eye from the nearest embankment (12). After four weeks (estimated hatching period), only ten nests were relocated by drone, due to vegetation overgrowth. All relocated nests were placed directly either within reed beds or on lower branches of shrubs, but always without higher branches obstructing the view from above. Finally, in the fledging period, no nest was relocated on drone imagery, due to further vegetation growth. Only 27 juveniles were found by drone, mostly perching on the canopy, without any evidence of nest failure, suggesting a critical underestimation. In conclusion, drone use improves accuracy of counting nesting Squacco Herons, but fails to assess productivity.
Whether mallard (Anas platyrhynchos) numbers have declined in recent years has been a subject of concern and debate among waterfowl biologists, wildlife managers, and administrators. Further controversy surrounds the reason for the presumed decline. One opinion holds that the decline, if it exists, is simply a reflection of a dry period, with fewer ponds available to support mallards. The opposing view is that mallards have declined more severely than wetland numbers, and have not responded to subsequent improvements in wetlands.
ResearchGate has not been able to resolve any references for this publication.