Tricolored Blackbird 2014 Statewide Survey Protocol

Thank you for your interest in participating in the 2014 Tricolored Blackbird Survey. Tricolor numbers have been declining alarmingly for the past decade, so the 2014 Survey may be especially important. The survey is conducted every three years in order to estimate population size and document trends in 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 many other concerned citizens 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. We will seek to comprehensively survey tricolors throughout their range during a brief 3 day interval to reduce the possibility of double-counting the same birds, and artificially inflating the estimate of the number of breeding birds.

I. Know your area: Scouting, habitats, sources of stored grains

It is very useful to plan and then review your survey route several days before the survey, especially if this will be your first time in your survey area. This will allow you to become familiar with the survey route as well as to anticipate where birds may and may not be found during the survey weekend based upon observations of occupied sites as well as by observations of appropriate nesting and foraging habitats. Tricolors nest in a wide variety of vegetation, but are most often found in freshwater marsh, Himalayan blackberry copses, weedy fields dominated by milk thistle and/or mallow and mustard, and grain fields (typically triticale) adjacent to dairies. The birds also forage in a wide variety of habitats, including dry and moist upland pastures, shrublands, alfalfa, and rice paddies but are especially attracted to stored grains associated with livestock (dairy cows, sheep, goats, horses). If your survey route includes sources of stored grains, be sure to check them for the presence of foraging birds. Should you see birds at sources of stored grains prior to or during the survey weekend, you may frequently be able to find colonies by following birds back from their foraging sites to their nesting locations. By April 1 many if not most colonies will be active in southern California, coastal areas, the San Joaquin Valley, the southern Sacramento Valley, and many foothill locations, but sites further north in the Sacramento Valley are typically not occupied until mid-to-late May.

II. Know your birds: Timing and Behavior

The 2014 survey occurs from April 18th to 20th and only observations made during this interval will be reported as part of the 2014 survey. Birds may shift locations over relatively short periods of time during the breeding season so it is essential that the survey is conducted during a brief interval. Subsequent observations made in the first few days after the Survey should also be noted and records entered via the Portal (http://tricolor.ice.ucdavis.edu).

The birds’ behavior changes dramatically depending upon the stage of the breeding cycle. When settling into a new colony, males are extremely vocal and active and move from perch to perch high in the nesting vegetation, often jostling with males on adjacent territories (ca. 2 days). At this time females move slowly and silently from one territory to another, often several feet below the displaying males. At nest building (3-4 days), the females fly actively from nesting vegetation to sources of nest materials (grasses and mud) and back again. They are silent but very conspicuous in the landscape. Males remain mostly on their territories perched atop the nesting substrate but display and call less frequently than during settlement. Territorial squabbles usually end by the time nests are built. Following nest-building, females sit out of sight and incubate their eggs (10-12 days) and both males and females are silent and inconspicuous. During the incubation stage, colony locations may appear unoccupied even when several thousand birds are present. It is for this reason that we recommend that all locations possessing appropriate nesting vegetation be observed for 15 minutes prior to concluding that the location is unoccupied. During the nestling stage (10-12 days), both parents forage for the young and form long flight lines of birds flying in single file (bill to tail) that may stretch for hundreds of yards and persist for several minutes as birds move from their nests to foraging destinations and back again. These foraging flight lines are often quite conspicuous in the landscape and it is often these foraging flight lines as they cross roads or other points of access that lead to colony discovery. At fledging and continuing for 4 days post-fledging, young perch and call conspicuously high in the nesting vegetation in large groups (“creches”) but these groups disperse after 4-6 days and small groups or single birds may be found far from the colony location foraging and being fed by the adults only a week after fledging.

III. Survey Locations and Priorities

Breeding colony locations have been plotted on maps to document known locations to enhance survey efficiency. These maps, and associated legends containing location names, are available for download from the Portal to Survey participants. Each volunteer team will survey a specific area within a county as determined with the county coordinator and survey for birds at known locations. However, team members should be alert for the presence of birds breeding in previously unknown locations, especially in regions between known locations, as conditions on the landscape change annually and birds respond quickly to landscape changes. It is especially important to document and thoroughly describe these new breeding locations. The Survey report form, also available for download from the Portal, contains all of the fields that are required to document and describe new colony locations. Records of new colony locations should be entered into the Portal as soon as possible.

IV. Survey Protocol

Viewing the colony

View all locations from the nearest public point of access. It is best to avoid any disturbance of nesting birds so do not approach occupied substrates and do not enter active colonies. 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 participant to determine how close is too close, but under most circumstances, colonies can be surveyed from 50-100 meters outside the boundaries of the vegetation in which the birds are nesting. Be alert for changes in the birds’ behavior, and if the birds appear defensive and are vocal, move back until their defensive behavior ends. Sometimes roadsides provide an elevated view of a colony, and thus a better perspective from which to estimate colony dimensions and numbers of birds. Similarly, the beds of pickup trucks or roofs of cars may provide an elevated perch from which to view colonies. Stand quietly and look both at the nesting substrate and at the surrounding area searching for departing or returning birds. Remember that during incubation, even occupied sites may appear to be unoccupied, so be sure to spend enough time at a site to be confident in your evaluation that birds are or are not present.

Private property should always be respected. Do not enter private property unless you have received permission from the landowner or have previously obtained permission to access.

Recording Site Names

When recording information, in all cases please use the location names given in the Portal. These are the names given on the location maps and associated legend files. If you observe birds in a new location, please provide an intuitive site name and directions. Geographic features and nearby roads make especially useful location names; for example, "St. Andrews Road" for a location adjacent to a road bearing this name, or "Owens Creek" for a site with a creek bearing this name flowing through it. Do not use the name of the landowner in the location name - most landowners are opposed to having their properties identified in on-line databases.

Recording Latitude and Longitude

Please record the latitude and longitude of all new locations and 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: 1) by entering a new location record into the Portal, and 2) by Google Earth. When entering a new location record in the Tricolored Blackbird Portal, scroll down to the Google Maps tool near the bottom of the Create Location form and zoom in and place a marker at the location of the colony. The latitude and longitude will automatically be entered when you do this. Be sure to record the coordinates in the Google Maps widget into the latitude and longitude fields above, right below the county name pulldown menu. Alternatively, use Google Earth and insert a placemark at the new colony location. The latitude and longitude will be recorded in the “Properties” of the placemark. Transfer this information into both longitude and latitude fields (on the upper Create Location form and in the Google Maps widget).

Duration of Observations

Be sure to record the amount of time you spend at each location whether occupied or not. It is recommended that you spend at least 15 minutes at each location. Locations that appear to be unoccupied may indeed be occupied by birds in the incubation stage of the breeding cycle, so be especially sensitive to the birds' behavioral changes that result from changes in the breeding cycle, with nest building and feed of young being especially active period and incubation being especially quiet and inactive. Getting good estimates of the numbers of breeding birds may take more than 15 minutes at occupied sites because if birds are active and there is a lot of movement to and from occupied substrates you may need to wait for birds to return to the breeding substrate after departing to obtain nesting material or food with which to feed the young.

Estimating Colony Size

Tricolored Blackbird colonies range in size from 20 to 20,000 birds. 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 and entered into the Portal.

Precise Counts

For small colonies (approximately less than 500 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, or 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 lines 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 some cases you may 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 birds has dropped off, 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 report form 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. It is often best to come up with an estimate and then continue to observe the birds keeping in mind your estimate and verifying that your estimate is consistent with the number of birds you're observing.

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. All colonies of 10,000 or more birds should immediately be reported to your county coordinator and to the Survey coordinator, Dr. Bob Meese, at rjmeese@ucdavis.edu

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 groups of males and females. A quick estimate 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.

Recording Colony Characteristics

Documenting absence from known locations and estimating colony sizes at occupied sites 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 colonies in new locations. The report form allows you to record both primary (dominant) and secondary substrates. Tricolored Blackbird native nesting habitat consists of young, rapidly-growing freshwater marsh dominated by cattails or tules, but birds also nest in a variety of other vegetation types including grain crops, particularly triticale fields in association with dairy farms in the San Joaquin Valley and southern California, Himalayan and California blackberry, milk thistle, mallow, mustard, stinging nettle, flooded small willows, flooded small cottonwoods, Arundo donax, desert olive, prickly lettuce, mule fat, coyote brush, raspberry, flooded tamarisk, and poison hemlock. One colony has even been established in a field of fava beans!

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). Foraging birds will fly up to 5 miles to sources of abundant food (like farms with stored grains), but most foraging occurs within 2 miles of colonies. Knowledge of locations of stored grains may 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).

Area of Nesting Substrate

Try to record the approximate length and width of 1) the breeding substrate available and 2) the breeding substrate utilized within each colony. These measures are used to estimate the amount of nesting substrate available and may also be used to provide a second estimate of the number of breeding birds. You may estimate the breeding substrate by while in the field by pacing out two sides of the colony or on a computer by using the ruler in Google Earth. The report form allows you to record these estimates.

Behavior and Colony Status

Please also record the behavior of the birds at a colony to help to document the stage of the breeding cycle. Researchers may use this information to examine trends in the timing of breeding. If possible, note the following behavioral classes at occupied locations:

  • Singing: pronounced to almost deafening chorus of males heard singing at a colony; indicates settlement
  • Carrying Nest Material: females observed carrying nest material (e.g. grass); indicates nest-building
  • Colony Quiet:males are not singing and relatively few birds are seen moving about; indicates incubation
  • Carrying Food: adults observed carrying food (usually insects protruding from bill); indicates nestling stage
  • Fledglings: recently fledged young observed out of nests, possibly in association with adults; indicates fledging and successful reproduction. Please try to estimate the number of fledglings!

Total Survey Time and Mileage

To help us to document the size of the Statewide Survey effort, please record the total time participants were in the field, the number of observers in your team, and the total number of miles driven while surveying. These estimates can be recorded separately and emailed to your county coordinator or to the Statewide Survey coordinator, Dr. Bob Meese (rjmeese@ucdavis.edu).