Avian ecology field methods
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.
Basic counts
Basic bird counts are a good way to estimate population 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 raptors, 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.
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 rate. 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 to monitor nest and record information about nest survival, 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.