Performing Department
Environmental & Forest Biology
Non Technical Summary
Despite ongoing management efforts at breeding colony sites, the federally-endangeredNorthwest Atlantic breeding population of roseate terns (Sterna dougallii) has declined morethan 20% since 2000. The results of an analysis from a 20-year study of adult survival, and areview of recent productivity data, strongly suggest that post-fledging survival during the firstyear of life could be a major factor limiting population recovery and driving the current decline;Building on our own recent work, we are proposing new research on what is occurring duringthe post-breeding dispersal period, after the Hatch Year birds (HYs) have fledged and movedaway from the breeding colonies, but before the birds depart the US on their migration to SouthAmerica. Preliminary results from our banding resight work have shown (a) high temporal andspatial variation in staging site use within and between years, and (b) virtually the entire NWAtlantic breeding population staged in and around southeastern MA during 2007-2009. During2008 and 2009, the majority of post-breeding terns, including roseate terns and common terns(Sterna hirundo, MA special concern) used only 2.4 km2 of Cape Cod National Seashore's(CACO) intertidal areas and beaches during the post-breeding staging period of July-October.We propose to (1) examine geographic and temporal variation in the use of these staging sitesby birds coming from breeding colonies in three areas (CT & NY; MA; NH, ME & Canada), (2)quantify rates and causes of naturally-occurring and human-related (including researcherinduced)disturbances at sites with varying levels of management, and (3) document effectsthat disturbances may have on the terns' behavior (especially behaviors influencing premigratorycondition and survival) and their use of CACO staging areas.Awarded Start Date: 6/11/14Sponsor: NPS
Animal Health Component
0%
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
There are several major objectives to the proposed work. The firstwill be to expand on prior work to provide more detail on temporal and geographic variation inthe use of post-breeding dispersal period daytime staging sites in CACO by HY roseates (andtheir care-giving parents) from throughout the breeding range. The results of the work by our"Resighting Team" are expected to be of value to determining the duration of risk of birds fromdifferent breeding colonies to various events (e.g., hurricanes, oil spills, etc.) that might affectthem while they are in this area.The second objective is to use long-distance observations by a "Disturbance Study Team" tocategorize and quantify both naturally occurring and human-related disturbances (includingresearch-induced disturbances resulting from Resighting Team. staff trying to get close enoughto identify individuals) of mixed-species flocks of staging terns. To accomplish this we plan todescribe and quantify flock reaction distances, disturbance responses, and, if possible,displacement distances (particularly of colorbanded roseate terns). We will also quantifyactivity budgets of adult terns and any effects of disturbance on those activity budgets.The third major objective (to be accomplished by the "Parental Care Study Team") is toestimate time-activity budgets of HY roseate terns, and the potential effects of disturbances onthem and on the cohesiveness of parent-offspring groups. Previous studies of (1) the relativeforaging success of HYs compared to that of adults during the post-breeding dispersal period(Watson and Hatch 1999), (2) observations of banded HYs from our area begging at adultswhile staging in Puerto Rico (Hays et al. 2010), (3) studies of closely related common terns byNisbet (1976) and Schauroth and Becker (2008), and (4) observations of sooty terns(Onychoprion fuscata) by Feare (2002), sandwich terns (Thalasseus sandvicensis) by Stienenand Brenninkmeijer (2002), royal terns (T. maximus) by Ashmole and Tovar (1968), andCaspian terns (Hydroprogne caspia) by Barlow (1998) provide evidence for the occurrence -and possibly even the need - for prolonged parental care in terns. Factors that lower theamount and/or rate of food provided by a care-giving parent during the post-breeding dispersalperiod might result in an increased probability of mortality of a HY tern, if not during the postbreedingdispersal period, than possibly during migration. In the following sections we providemore detail on the objectives and methods.
Project Methods
Methods: Most young chicks will be banded within a few days of hatch at participatingcolony sites so that they can still be positively identified as belonging to a particular nest andparents. In addition to the use of a standard USGS Bird Banding Laboratory (BBL) band onone leg, a 3-character engraved 7.5-mm tall PFR colorband (using one of three base colorsdepending upon the regional location of the colony site) will be placed on the opposite leg.Each year in 2013 and 2014, one color will be used on at least 250-300 chicks from colonysites in NY and CT, a second color will be used on about 250-300 chicks from NH, ME, andNova Scotia (Canada), and a third color will be used on chicks from MA. Chicks not receiving aPFR will receive a metal FR band as is the current practice. Given the typical expectedmortality of chicks prior to fledging (Nisbet et al. 1999), this scheme will allow observers atstaging sites to quickly identify the source area of about 800 or more colorbanded HYs eachyear.Resightings and identifications of individually colormarked terns on CACO and other stagingsites will be made by the ResightingTeam consisting of up to 10 observers (Spendelow,MACWP staff, a M.Sc. student and 7 technicians - with a subset of these also on theDisturbance Study Team) using spotting scopes and recording devices from mid-July toSeptember each year. The timing and duration of observation sessions will depend in part onweather and tidal conditions, the number of colorbanded terns present, and how long theyremain at each site each day. Previous work has shown great temporal and spatial variation intern abundance, so flexibility is needed in site coverage. To examine temporal variation in therelative importance to roseate terns of CACO staging sites over the course of the entire postbreedingdispersal period, and to detect movements that might result from a major disturbanceat one site, near complete coverage of all sites on a daily basis is critical for the resighting anddisturbance analyses. Because prior work by MACWP and USGS showed that roseate ternsfrequently move between staging sites and some locations are difficult to access, a ResightingTeam of this size is necessary to ensure successful data collection by the Disturbance andParental Care Teams. Resighting Team information can help the Disturbance Team choosedaily study sites where they can incorporate observations of research-induced disturbance. Atthe same time, because the Disturbance Team staff will usually be too far away to identifyindividuals, Resighting Team data are needed to allow us to detect separations of individualadults and their HYs that might be attributable to any of several sources of disturbance.Once a flock is located, observers slowly walk, wade, or kayak to approach and remain closeenough (usually within 40 m) of the shifting birds to make identifications. Because stagingflocks are often in a state of flux, observers for this objective must continue to makeidentifications until the flock has departed or they stop seeing new colormarked individuals.Colorband combinations and unique colorband codes are recorded on handheld devices. Dataon flock size, species composition, and age structure based on total terns (if less than 200) orscan-samples (for larger flocks) will be recorded at the beginning of each session and again ifmajor changes occur. Formal multisite mark recapture/resighting modeling approaches(Spendelow et al. 2002, 2008) will be adapted for use in estimating staging site movementrates, fidelity, and stopover duration.Methods: Flocks will be observed by the Disturbance Team using binoculars and a spottingscope from a distance that does not affect the behavior of the terns (at least 100 m) for up tothree 2.5-hour sessions daily at one or two sites. The observers will record their own positionusing a GPS, and the bearing and distance to the flock using a compass and a rangefinder.Data on flock size, composition, and dispersion (e.g., single large flock vs. several scatteredsubflocks) will be recorded every five minutes. The behavior of a sample of randomly-selectedfocal birds (both adults and HYs) also will be recorded every five minutes. We will collect dataon time-activity budgets (the proportion of time roseate terns spend in behaviors such aspreening, resting, reacting to disturbance), and will categorize and record the numbers ofdisturbance sources. In order to quantify adult activity budgets, one observer per day willconduct focal individual sampling on individually-marked birds and continuously recordprovisioning events, prey size and species (if possible), and occurrence of alert and aggressivebehaviors; this observer also will sample general behavior type (rest, fly, preen, feed, walk)every 10 seconds. This observer will attempt to sample many different birds in the flock beforemoving to a new site that day. A second observer will use flock-level behavioral samplingtechniques to continuously record potential disturbance types and the flocks' reaction to them.All potential disturbances within 500-1000 m of the flock will be recorded, and the distance andbearing from the observer to the disturbance source will be measured using a compass and arangefinder. The closest distance to the flock that moving objects attain will be recorded, aswell as the distance that elicits a response, if any. Behavioral responses of flocks to potentialdisturbance events will be classified as (a) no response, (b) birds start or increasevocalizations and may walk away, but do not fly off, (c) some, but not all, members of the flockmay fly up, but settle again within one minute (d) most/all members of the flock fly up and stayin the air for 1-5 minutes, (e) birds fly up in a 'panic flight' or 'dread flight' during which mosteither stay high aloft for more than five minutes or (f) birds fly up and leave the area. Responseduration will be recorded, and displacement distance if the flock moves but remains in sight willbe measured by taking a new bearing and measuring the distance to the flock with arangefinder. At the beginning of each sampling period, the following covariates will berecorded: presence of ongoing events within 150 m of the focal individual(s), behavioral statefocal individual(s), age (estimated or known), species composition of flock, habitat, time of day,tidal state, temperature, precipitation, wind direction/velocity, and % cloud cover.We will compare the proportion of time roseate terns spend in different behaviors among sitesand the amount of time in different behaviors before, during, and after disturbance events. Wewill compare the number of disturbances per hour, the number of reactions per hour, theproportion of disturbances causing a response of each type, the response duration, thereaction distances, and the displacement distances among disturbance categories and amongsites with different levels of management and protection.Methods: Methods and analyses for this objective will be identical to those in objective 2,except this team will focus focal behavioral observations on HYs. In addition to the behaviorsidentified above, the observer will also record continuously all instances of begging by HYs.Further, whenever possible, the identities of provisioning parents of focal HYs will be recorded,or the adult targets of begging, so that we can identify the relative roles of males and femalesin post-fledging parental care, and any effects of disturbance on disrupting parent-fledglinginteractions.