Avian ecology field methods
Encyclopedia
There are many field methods available for conducting avian
ecological
research. They can be divided into three types: counts, nest
monitoring, and capturing and marking.
size, detect changes in population size or species
diversity, and determine the cause of the changes if environmental
or habitat
data is collected as well. Basic bird counts can be completed fairly easily and inexpensively, and they provide general information about the status of a bird population.
Birds can be directly counted on breeding colonies, and at roosts, flocks, or Leks. Large diurnal
migrants, like many raptor
s, can be counted as they pass through migration
bottlenecks. Small nocturnal migrants are harder to count, but many advances have been made in the use of radar
and microphone arrays to identify and count them.
. Nests can be found either through systematic searching of the birds’ preferred habitat or by watching birds for behavioral clues. A researcher can then track the success of each nest by regularly checking nests for signs of hatching
, fledging
, or predation
.
Nest monitoring can also provide extremely valuable information about nesting behavior, habitat selection, and nest predation. Cameras can be used to study bird nesting behaviors, or even to catch nest predators in the act. The timing of breeding in relation to weather variables can be studied, as well as the size of eggs and chicks in relation to food quality and abundance. Records of habitat variables at each nest provide helpful information on the birds’ nest site selection criteria, and maps of all nests found in a study area allow for examination of how territories are distributed through the habitat.
tags, or dyes which allow the bird to be recognized in the field without requiring recapture. Finally, a bird may be outfitted with a radio or satellite transmitter, which enables the bird to be tracked as it moves around within the local landscape or even as it migrates around the world.
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
ecological
Ecology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...
research. They can be divided into three types: counts, nest
Bird nest
A bird nest is the spot in which a bird lays and incubates its eggs and raises its young. Although the term popularly refers to a specific structure made by the bird itself—such as the grassy cup nest of the American Robin or Eurasian Blackbird, or the elaborately woven hanging nest of the...
monitoring, and capturing and marking.
Basic counts
Basic bird counts are a good way to estimate populationPopulation
A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...
size, detect changes in population size or species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
diversity, and determine the cause of the changes if environmental
Environment (biophysical)
The biophysical environment is the combined modeling of the physical environment and the biological life forms within the environment, and includes all variables, parameters as well as conditions and modes inside the Earth's biosphere. The biophysical environment can be divided into two categories:...
or habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
data is collected as well. Basic bird counts can be completed fairly easily and inexpensively, and they provide general information about the status of a bird population.
Birds can be directly counted on breeding colonies, and at roosts, flocks, or Leks. Large diurnal
Day
A day is a unit of time, commonly defined as an interval equal to 24 hours. It also can mean that portion of the full day during which a location is illuminated by the light of the sun...
migrants, like many raptor
Bird of prey
Birds of prey are birds that hunt for food primarily on the wing, using their keen senses, especially vision. They are defined as birds that primarily hunt vertebrates, including other birds. Their talons and beaks tend to be relatively large, powerful and adapted for tearing and/or piercing flesh....
s, can be counted as they pass through migration
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
bottlenecks. Small nocturnal migrants are harder to count, but many advances have been made in the use of radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
and microphone arrays to identify and count them.
Point counts and area searches
Perhaps the simplest method of counting birds is called a "point count", in which a trained observer records all the birds seen and heard from a point count station for a set period of time. A series of point counts completed over a fixed route can then be compared to the results of the same point counts in other seasons or years. A similar method, called an area search, involves searching throughout a fixed area for a set amount of time and recording the number of birds seen and heard.Nest monitoring
Nest monitoring is essential for measuring the reproductive success of a population, which is important for identifying changes in a population’s birth rateBirth rate
Crude birth rate is the nativity or childbirths per 1,000 people per year . Another word used interchangeably with "birth rate" is "natality". When the crude birth rate is subtracted from the crude death rate, it reveals the rate of natural increase...
. Nests can be found either through systematic searching of the birds’ preferred habitat or by watching birds for behavioral clues. A researcher can then track the success of each nest by regularly checking nests for signs of hatching
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
, fledging
Fledge
Fledge is the stage in a young bird's life when the feathers and wing muscles are sufficiently developed for flight. It also describes the act of a chick's parents raising it to a fully grown state...
, or predation
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
.
Nest monitoring can also provide extremely valuable information about nesting behavior, habitat selection, and nest predation. Cameras can be used to study bird nesting behaviors, or even to catch nest predators in the act. The timing of breeding in relation to weather variables can be studied, as well as the size of eggs and chicks in relation to food quality and abundance. Records of habitat variables at each nest provide helpful information on the birds’ nest site selection criteria, and maps of all nests found in a study area allow for examination of how territories are distributed through the habitat.
Capturing and marking
Capturing and marking birds allows for individuals to be identified whenever or wherever they are captured or seen again. It is a powerful method for studying bird migration, estimating population sizes and survival rates, and recognizing changes in productivity. There are many different ways to capture birds, but the most widely used method is a mist-net, a net made of fine nylon mesh which is nearly invisible. Birds fly into the net, becoming entangled, and are extracted by researchers. Birds can then be identified, measured, weighed, and marked with a small aluminum band bearing a unique number. The number is reported to a central database so that information about the bird can be updated if the bird is ever recaptured somewhere else. Birds may also be marked with a locally unique combination of colored plastic leg bands, leg flags, patagialPatagium
*In bats, the skin forming the surface of the wing. It is an extension of the skin of the abdomen that runs to the tip of each digit, uniting the forelimb with the body.*The patagium of a bat has four distinct parts:...
tags, or dyes which allow the bird to be recognized in the field without requiring recapture. Finally, a bird may be outfitted with a radio or satellite transmitter, which enables the bird to be tracked as it moves around within the local landscape or even as it migrates around the world.
See also
- Australian Bird CountAustralian Bird CountThe Australian Bird Count was a project of the Royal Australasian Ornithologists Union . Following the first and successful Atlas of Australian Birds project, which led to the publication of a book on the distribution of Australian birds in 1984, it was suggested by Ken Rogers that the RAOU...
(ABC) - Breeding Bird SurveyBreeding Bird SurveyA breeding bird survey monitors the status and trends of bird populations. Data from the survey are an important source for the range maps found in field guides. The North American Breeding Bird Survey is a joint project of the United States Geological Survey and the Canadian Wildlife Service...
- Christmas Bird CountChristmas Bird CountThe Christmas Bird Count is a census of birds in the Western Hemisphere, performed annually in the early Northern-hemisphere winter by volunteer birders...
(CBC) (in the Western Hemisphere) - Seabird Colony RegisterSeabird Colony RegisterThe Seabird Colony Register is a database, managed by the British Joint Nature Conservation Committee, which contains counts of breeding seabirds at British seabird colonies made between 1969 and 1998, which is used for analysing past changes in breeding seabird numbers and changes in their colony...
(SCR) - The EBCC Atlas of European Breeding BirdsThe EBCC Atlas of European Breeding BirdsThe EBCC Atlas of European Breeding Birds - their distribution and abundance is an ornithological atlas published for the European Bird Census Council by T & A D Poyser in 1997. Its editors were Ward J. M. Hagemeijer and Michael J. Blair. The atlas was the first to present grid-square distribution...
- Tucson Bird CountTucson Bird CountThe Tucson Bird Count is a community-based program that monitors bird populations in and around the Tucson, Arizona, USA metropolitan area...
(TBC) (in Arizona in the US)