Lecture 03 – January 15, 2024 Field Methods I

Question 1

Census Count:

Answer 1

This is a direct method involving an actual headcount of all individuals in a population. It is the most accurate but often difficult due to factors such as large population sizes and inaccessible habitats.

Question 2

Population Estimate:

Answer 2

This method uses sampling techniques to estimate population size. It includes capturing and marking a subset of the population, then later recapturing individuals to estimate the total population based on the proportion of marked to unmarked individuals.

Question 3

Population Index:

Answer 3

An indirect measure of population abundance that does not attempt to estimate actual numbers. This could be based on signs or products of the population, such as tracks, nests, or droppings. It’s useful for tracking trends over time.

Question 4

Questions Wildlife Managers Address:

Answer 4

What is the status of the population (increasing, decreasing, stable)?
What is the population structure in terms of age or sex ratio?
What are the population’s survival and reproductive needs?
What factors affect survivorship and mortality rates?
How healthy are individuals in the population?
How interconnected are their habitats?

Question 5

Approaches to Measuring Population Size:

Answer 5

Census count: A complete headcount, which is often challenging due to various factors such as animal behavior or habitat.
Population estimate: Involves sampling methods like mark-recapture to estimate total population size.
Population index: Provides an indication of population abundance without an attempt to estimate actual numbers, using evidence of animal presence such as tracks or vocalizations.

Question 6

3. Identify characteristics that makes wildlife hard to find or count.

Answer 6

Animals may be difficult to locate.
They might move too much, making counting challenging.
They may congregate in large numbers.
They are often spread across large, poorly-defined areas.

Question 7

For the methods of estimating population size that we had discussed in class, identify when it is appropriate to use each method.

Answer 7

Census counts are suitable when a complete count is possible.
Population estimates like mark-recapture are used when a sample can represent the whole.
Population indices are useful for indirect measures and trend analysis when counting is impractical.

Question 8

Describe the mark-recapture method (with emphasis on how to mark individuals)

Mark-Recapture Method:

Answer 8

This method involves capturing animals, marking them in a way that does not harm or alter their behavior, and then releasing them back into their environment. After a period of time, a second capture is made, and the proportion of marked to unmarked individuals is used to estimate the total population size. Marks can be physical tags or natural markers.

Question 9

describe the line transect method for estimating population size

Answer 9

Line Transect Method:
This involves walking a predetermined path and counting the individuals observed. The distance from the path to the individuals is also recorded, allowing for the calculation of population density using statistical methods like the King Method, which considers the effective width of the transect.

Question 10

calculate population size using the Petersen and King methods. You should independently think about how you would use the King Method when habitat is heterogeneous.

Answer 10

Question 11

Explain the assumptions of the mark-recapture method and the line transect method of estimating population size, and how to ensure that these assumptions are not violated.

Explain the assumptions of the mark-recapture method

Answer 11

The assumptions for both mark-recapture and line transect methods are crucial for accurate population size estimates.

For the mark-recapture method, it’s assumed that marks are not lost or overlooked, that marked individuals mix randomly with the unmarked population, and that there is no differential survival between marked and unmarked individuals. To ensure these are not violated, methods of marking should be secure and recognizable, and sufficient time should be allowed for the animals to mix back into the population.

Question 12

Explain the assumptions of the mark-recapture method and the line transect method of estimating population size, and how to ensure that these assumptions are not violated.

Explain the assumptions of the line transect method

Answer 12

For the line transect method, it is assumed that all animals on the line are detected, and that animals are detected at their initial location, without being disturbed by the observer’s approach. To maintain these assumptions, observers must be well-trained in spotting animals and estimating distances accurately, and care must be taken to minimize disturbance.

Question 13

Describe and differentiate the Waterfowl Breeding Population and Habitat Survey, the Breeding Bird Survey, the Audobon Christmas Bird Count, and the Great Backyard Bird Count.

Waterfowl Breeding Population and Habitat Survey:

Answer 13

The Waterfowl Breeding Population and Habitat Survey, Breeding Bird Survey, Audubon Christmas Bird Count, and Great Backyard Bird Count are all programs designed to monitor bird populations, but they differ in methodology and timing.

Focuses on the breeding populations of waterfowl in North America to inform management and conservation efforts.

These surveys contribute valuable data for the conservation and management of bird populations.

Question 14

Describe and differentiate the Waterfowl Breeding Population and Habitat Survey, the Breeding Bird Survey, the Audobon Christmas Bird Count, and the Great Backyard Bird Count.

Breeding Bird Survey:

Answer 14

The Waterfowl Breeding Population and Habitat Survey, Breeding Bird Survey, Audubon Christmas Bird Count, and Great Backyard Bird Count are all programs designed to monitor bird populations, but they differ in methodology and timing.

Breeding Bird Survey: An annual survey that tracks the status and trends of bird populations across North America, conducted during the breeding season.

These surveys contribute valuable data for the conservation and management of bird populations.

Question 15

Describe and differentiate the Waterfowl Breeding Population and Habitat Survey, the Breeding Bird Survey, the Audobon Christmas Bird Count, and the Great Backyard Bird Count.

Audubon Christmas Bird Count:

Answer 15

The Waterfowl Breeding Population and Habitat Survey, Breeding Bird Survey, Audubon Christmas Bird Count, and Great Backyard Bird Count are all programs designed to monitor bird populations, but they differ in methodology and timing.

Audubon Christmas Bird Count: A citizen-science survey held annually during the Christmas season, where volunteers count birds within specified circles.

These surveys contribute valuable data for the conservation and management of bird populations.

Question 16

Describe and differentiate the Waterfowl Breeding Population and Habitat Survey, the Breeding Bird Survey, the Audobon Christmas Bird Count, and the Great Backyard Bird Count.

Great Backyard Bird Count:

Answer 16

The Waterfowl Breeding Population and Habitat Survey, Breeding Bird Survey, Audubon Christmas Bird Count, and Great Backyard Bird Count are all programs designed to monitor bird populations, but they differ in methodology and timing.

Great Backyard Bird Count: An annual count for all levels of bird watchers where individuals report the number and species of birds seen during a four-day period in February.

These surveys contribute valuable data for the conservation and management of bird populations.

Question 17

Describe how roadkill counts can be used to generate population sizes for wild populations.

Answer 17

Roadkill counts can be used as a population index to estimate the abundance of wildlife. By counting the number of animals killed on roads, researchers can infer population trends. This method assumes a consistent detection rate and that roadkill numbers are proportional to the population size. However, it requires adjustments for factors like traffic volume, animal behavior, and the likelihood of animals crossing roads. Roadkill data must be interpreted with caution, as it may not reflect true population sizes but can signal changes or trends.