Tricolored Blackbird Portal

Thank you for volunteering to participate in the 2008 Tricolored Blackbird Survey. This survey is conducted every three years in order to estimate population size and track changes in the status of the Tricolored Blackbird population. This information is critical for guiding our conservation efforts and could not be accomplished without your help and the extensive efforts of other citizen scientists across the state. The following protocol outlines the methods to be used during the survey and how to report your observations.

Our goal is to develop the best estimate of the statewide population as possible. The more areas that are surveyed where the presence and number (or absence) of Tricolored Blackbirds is recorded, the better the estimate will be.

I. Scouting

It is very useful to check on nearby sites and search the surroundings before the dates of the official survey. This will streamline the survey and allow you to spend more time at the colonies that require the most effort to observe and count. By April 1 most colonies will be active for their first round of breeding. In the more southerly colonies some nests will already have hatched young. It appears that 2008 is an ‘early’ year for Tricolors. Estimating the colony size and observing the behavior and habits of the Tricolored Blackbirds at this point is interesting and good practice.

II. Timing

The 2008 survey window is April 25th to 27th. All observations that will be reported as part of the 2008 survey should be carried out on one or more days between April 25 and 27. Tricolored Blackbirds and colonies can shift locations over relatively short periods of time during the breeding season. Making sure that a comprehensive count is made in a narrow time window helps ensure we are not counting the same birds more than once.

Subsequent observations at any future date should also be noted and can be submitted vai the Tricolored Blackbird Portal (http://tricolor.ice.ucdavis.edu).

III. Survey Locations and Priorities

Breeding colony locations are on maps provided to you were all discovered on previous censuses dating back to the early 1990’s, or incidentally discovered and documented at other times. Some sites were found during the last statewide census in 2005. Each volunteer team has been asked to survey a specific area within their county and, in most cases, to visit specific colony sites that were reported in 2005. The following are the areas that should be surveyed in priority order:

Ideally you are already familiar with these former colony locations, but if not, the locations of 2005 colonies and other reported sites should be easy to find from the maps we provide.

IV. Survey Protocol

Viewing the colony

In general, it is best to avoid any disturbance of nesting birds, as the disturbance can cause nest failure. This is especially true for Tricolored Blackbirds and other colony nesting species, since pairs are in close proximity to each other, and single disturbance can cause the failure of many nests. Under no circumstances should volunteers enter the colony. Colonies should be surveyed from a distance at which the birds are unaffected by the surveyor’s presence. Since colonies may be located in a variety of contexts, it is up to the observer to determine how close is too close. Under most circumstances, colonies can be surveyed from just outside the boundaries of the vegetation in which the birds are nesting. The majority of sites will be readily viewable from public roads and allow close and thorough study. Sometimes roadsides provide an elevated view of a colony, and thus a better perspective from which to estimate colony dimensions and numbers of birds.

Private property should also be respected. Do not enter private property unless you have received permission. A Fact Sheet about the survey has been prepared and is available for you to give interested landowners (or others) to inform them about the survey.

Colony Name

Use the colony name given in the list of 2005 colonies that you have been provided and that are used to label the colony on the maps (if you have been assigned to specific colonies). If this is anew colony (not already entered in the online database and not in the list of colonies provided, then please give the site a logical name. Be sure to not use the name of the private landowner unless you have permission. Also, please provide directions to the site (if this is a new colony), with enough detail that another observer could get to that location.

Latitude and Longitude

If this is a known colony that you have been assigned to visit, no need to record the site coordinates. For new colony sites, if you have a GPS unit, please use it to collect and record the latitude and longitude of the site during the survey. Record the datum used by the GPS unit (the default for most GPS units is WGS84, but in some cases they may be set to NAD83). If you do not have a GPS unit there are two ways to identify and record the coordinates. First, when entering your new location on the Tricolored Blackbird Data Portal, you can use the built-in Google Maps tool to zoom in and place a marker at the location. The latitude and longitude will automatically be entered when you do this. Alternatively, you can use Google Earth, an extremely useful and user friendly, free global mapping tool. Search for and zoom into the location in Google Earth. Insert a placemark at the location (be sure to move the marker to the actual spot) and the latitude and longitude will be recorded in the “Properties” of that marker.

Duration

Be sure to record the amount of time you spend at each colony site (including those where there are no Tricolored Blackbirds this year). Spend as much time at each colony as you need to get your best estimate of the number of birds. If after 10 to 15 minutes at a known colony site you have not seen any Tricolored Blackbirds, move on to survey new sites or areas. If Tricolored Blackbirds are present, use your own judgment about how much time to spend at the colony. In general, prolonged viewing of a colony will improve your estimate and the larger the colony the more time should be spent. This is particularly true for very large colonies (> 10,000) where it may take some time to evaluate the number of birds. With such large colonies, the more time you spend at the colony, the more the apparent chaos will give way to a semblance of order, enabling you to better estimate the size of the colony and gather observations of singing males, nest-building females, adults feeding chicks, or fledglings.

However, the time spent at one colony is at the expense of visiting more areas and documenting additional colonies. Do not spend too much time at small colonies where you can estimate the number of birds quickly. In this case, finding and counting new birds will be more valuable for the statewide estimate.

Colony Size

A Tricolored Blackbird colony can range from 20 birds to 100,000 or more birds. For this survey, all estimates will be based on visual counts of the birds at a colony. For small colonies, precise counts can be made, but in larger colonies a visual estimate will be necessary. The method used should be indicated on the data sheet.

Precise Counts

For small colonies (approximately less than 200 birds), a precise count of the number of birds will usually be feasible. With care, this should provide a very precise estimate of the number of birds present.

Scanning Surveys

When large numbers of birds are streaming by, dropping into vegetation, and are otherwise extremely active, precise counts will be impossible. To estimate the number of birds in large groups during this survey there are two ways to estimate number depending on whether birds are flying by or within the colony.

1. Within the colony: for birds that are perched or flying around within the colony, it is effective to count the number of birds that fill a specific, repeatable field of view, such as the field of view in your binoculars. Within this field of view, either count precisely or by fives or tens for more dense concentrations, to obtain a reasonable estimate of the number of birds within that view. Then, multiply that number by the number of fields of view that comprise the entire flock or colony.
2. Flying in Transit: Depending on the time of day and colony status, there may be streams of birds flying between the colony and an off-colony food or water source. In this case, the number of birds in these flight paths can be estimated by counting the number of birds that move by in a given amount of time and multiplying this by the total time it takes for the flock to pass.

In many cases observers will need to employ both strategies. Position yourself somewhere with good visibility and use a timed count of the flying birds as they leave the colony. Once the flow of leaving birds has dropped off, then conduct a scanning count of the visible birds remaining within the colony itself. The scanning count of the colony should be repeated a few times to improve the estimate. Add the estimate of birds flying away from the colony to the count of birds within the colony. There is space on the data sheet to record your best estimate of birds, as well as what you think the minimum and maximum number of birds are at the colony. These minimum and maximum estimates will give us some sense of how accurate you feel your best estimate is.

Estimating the size of large colonies can be very challenging, and for some, frustrating. Remember that you are providing us with an approximation of colony size and not an exact count. All large colonies that you find will be revisited by one or more experts, regardless.

Sex Ratio

The accuracy of the count will also depend on the sex ratio of birds observed and this depends on activity at the colony. Some colonies that are just forming will have both males and females active so that most individuals can be seen. Once incubation begins however, it will be mostly males that are seen. This information is critical to record. The data sheet includes space for specifying the ratio of males to females seen and whether the colony is active but quiet (indicating incubation may have begun). Tricolored Blackbird flocks often separate into groupsof males and females. A quick estimation of the numbers in each sub-flock can be used to determine an overall sex ratio. Estimate the ratio of males to females in several sub-flocks or fields of view and average them to come up with an estimate.

Colony Observations

Locating new colonies and estimating colony sizes are the primary goals of the survey; however, the characteristics of colonies, the surrounding environment, and the behavior of the birds are all valuable for assessing the status and health of colonies.

Nest Substrate

Observers should record the nesting substrate of observed colonies. There is space on the data sheet to record both primary (dominant) and secondary substrates. Tricolored Blackbird native habitat consists of young, freshwater marsh dominated by tules or cattails, but they also nest in a variety of other vegetation types that provide enough structure and cover to build nests. In addition, they also now regularly nest in grain crops, particularly triticale fields in association with dairy farms. Likely substrate plants are: bulrush/tule, cattails, blackberry, milk thistle, nettle, and grains like triticale, wheat and barley. Other substrates include: willows, cottonwood, Arundo, desert olive, mustard, prickly lettuce, mule fat, coyote brush, raspberry, rice, tamarisk, and poison hemlock.

Colony Surroundings

In addition to locating and viewing the colony, it is useful to describe the surroundings. In addition to nesting substrate, Tricolored Blackbirds also require a source of open water and suitable foraging areas (e.g. upland pasture, grassland, alfalfa). They can fly several miles to sources of abundant food (like farms with stored grains). Knowing about these locations will assist in future surveys and may help observers find additional breeding colonies as birds move between various nesting sites and a centralized food source. Any stream of blackbirds is worth following! On the data sheet, if source of water or stored grains are identified, please record the presence of stored grains nearby and the distance to water. Also, note the dominant land use surrounding the colony (type of agricultural crop, natural vegetation type, etc).

Colony Area

Observers should try to record the approximate length and width of the breeding substrate within the colony. These measures will be used to calculate the total area of the colony. Since breeding substrate often occurs in patches over a larger area, size estimation is approximate. Colony area will be used with what is known about the average nest density within Tricolored Blackbird colonies to develop a secondary estimate of the number of birds in the colony.

• Measuring Width and Length: Where possible, observers should pace out two sides of the colony, using strides that approximate one meter. Record the number of meters for these two sides on the data sheet.
• Aerial Photos: Using satellite photos that are provided, observers can highlight the boundaries of the colony being used. These marked-up photos should be sent in with paper copies of datasheets following the surveys. These will provide a means for mapping the extent and calculating the total area of colonies observed.

Behavior and Colony Status

Behavior of birds at a colony and the current activity at the colony are also important sources of information for understanding the seasonal timing of breeding and success of particular colonies. Important observations to record on the datasheet include:

• Singing: pronounced chorus of males heard singing at a colony
• Carrying Nest Material: females observed carrying nest material (e.g. grass)
• Colony Quiet: if the colony is relatively quiet (no singing or large groups of males and females moving about) and primarily males are visible, this may indicate that incubation has begun and females are on nests.
• Carrying Food: adults observed carrying food (usually insects protruding from bill)
• Fledglings: observed young birds in association with adults.

Mapping New Colonies

In order to better ensure that we record the location of new colonies accurately, please use the street and colony maps provided (or another map you have available and can copy) to mark the location of new colonies you find and visit. These will be stored and used later for data quality checking.

Survey Routes

Using the maps provided or other maps you have available to indicate the routes taken during the survey by highlighting the roads and areas surveyed. These should be sent in with the datasheets and aerial photos following the survey.

Total Survey Time and Mileage

Please record the total time, number of observers in your team, and miles you drove for the survey. These can be recorded separately and emailed to Rodd Kelsey (rkelsey@audubon.org)