DOI: 10.5061/dryad.z34tmpgpx
title: Stopover regions, phenology, and spatiotemporal group dynamics of adult and juvenile Common Terns (Sterna hirundo) from inland lakes in North America

description: Understanding the behavior of migratory birds can help determine levels of
 connectivity and inform conservation actions for species of conservation
 concern. The Common Tern (Sterna hirundo) is a long-distance migratory
 seabird that is considered a species of conservation concern in the North
 American Great Lakes region and that has experienced significant declines
 in breeding numbers across large lakes in Manitoba. To better understand
 the movement ecology of Common Terns, we used data from multiple tracking
 technologies (solar geolocation, GPS tracking, and Motus radio tracking)
 obtained from individuals (n = 83) across five breeding colonies on four
 inland lakes in North America. We identified key stopover regions used
 during southward migration and explored how demographics and social
 interactions influence connectivity. We identified three key stopover
 regions (Lake Erie, the southern Atlantic Coast, and Florida) and
 documented, for the first time, differences in post-natal and
 post-breeding migration for inland nesting terns. Juveniles arrived, on
 average, three weeks later than unrelated adults to their first major
 staging area. Although adult female arrival to and departure from Lake
 Erie was similar to adult males, female schedules became significantly
 earlier than males as southward migration progressed. Using a graph
 network to describe the spatiotemporal associations among adults from the
 same inland lake, individuals appeared to be highly connected, meeting up
 in different regions throughout the non-breeding season, suggesting that
 social interactions may play an important role in maintaining spatial
 connectivity. Despite differences in migration schedules by sex and
 arrival to the first major staging area by age class, birds appeared to
 rely on the same key stopover regions during southward migration. The
 stopover regions identified in this study can help identify potential
 bottlenecks and guide future research aimed at assessing the impacts of
 climate change and human disturbance on Common terns breeding in North
 America.
description: Tracking devices (solar geolocators (GLS), GPS tags, and radio
 transmitters) were deployed on Common Terns nesting at five breeding
 colonies at inland lakes in North America. GLS data were processed using
 the R package TwGeos (Lisovski 2016) and FLightR (Rakhimberdiev and
 Saveliev 2016). Data downloaded from GPS tags did not require any
 additional processing. Data was downloaded from radio transmitters via the
 Motus Network and filtered using processes recommended in Brzustowski and
 LePage (2019). We summarized GLS and radio transmitter data occurring
 within high use areas to describe phenology of southward migration. GPS
 tag data were used to describe the strength of connectivity among
 individuals during the non-breeding season depicted using a simple
 interaction network.
description: # Stopover regions, phenology, and spatiotemporal group dynamics of adult
 and juvenile Common Terns (Sterna hirundo) from inland lakes in North
 America
 [https://doi.org/10.5061/dryad.z34tmpgpx](https://doi.org/10.5061/dryad.z34tmpgpx) ## Description of the data and file structure Tracking devices were deployed on Common Terns between 2013 - 2020 to document movement of adult and juvenile birds from inland lakes in North America. ### Files and variables #### File: geos\_phenology\_map.csv **Description:** This file contains solar geolocation tracking data for Common Terns breeding at inland lakes in North America. For each bird (tag_ID), information as to where the bird was breeding at the time of deployment (lake) is provided, as well as the sex of the individual (sex). The Arrival and Departure columns provide the first and last detection dates for individual birds occurring within the three defined stopover locations (region). Solar geolocation data was used to describe the southward phenology of Common Terns within the three defined regions by sex. ##### Variables * region: Locations where solar geolocation tracking data were summarized. This includes Lake Erie, the Atlantic Coast, and Florida. * lake: Location of the breeding colonies where Common Terns were fitted with solar geolocators for this study. This includes only the name of the lake where the tags were deployed (Lake Winnipeg, Lake Superior, Lake Huron, and Oneida Lake), not the specific colony name. * arrival: Date when a bird fitted with geolocators were first detected within a specified stopover region (i.e. Location). Format: mm/dd/yyyy. * departure: Date when a bird fitted with geolocators were last detected within a specified stopover region (i.e. Location). Format: mm/dd/yyyy. * tag_ID: Unique identification number associated with each solar geolocator. This number was used to identify individual birds fitted with solar geolocators. * sex: The sex of each individual bird fitted with a solar geolocator. Sex was determined by blood sampling or morphometrics. F = female, M = male, and U = unknown. #### File: gps\_network.csv **Description:** This file contains global positioning system (GPS) tracking data from Common Terns breeding in western Lake Superior. For each bird (tag_ID), information as to where the bird was breeding at the time of deployment (colony) is provided, as well as the sex of the individual (sex). The date and time columns describe when a GPS fix occurred. The quality/accuracy of each GPS fix is described by the number of satellites (sats) used to determine the position of a fix and the horizontal dilution of precision (HDOP). The specific model of GPS tag (gps_model) is also provided for each bird. GPS data from this study were used to describe the connectivity of individuals during the non-breeding season using network analyses to describe interactions. ##### Variables * gps_model: Refers to the specific model of global positioning system (GPS) tags deployed on Common Terns. This includes Swift or Standard.  * tag_ID: Unique identification number associated with each GPS tag. This number was used to identify individual birds fitted with GPS transmitters. * colony: Name of the breeding colonies where Common Terns were fitted with GPS tags for this study. GPS tags were only deployed on Common Terns nesting on Lake Superior and included Interstate Island (Interstate) and Ashland Island (Ashland). * sex: The sex of each individual bird fitted with a solar geolocator. The sex of all individuals fitted with GPS tags was determined by blood sampling (F = female, M = male). * date: Date of GPS fix (yy/mm/dd). All GPS units were scheduled to take a fix based on identical schedules.  * time: Time of GPS fix (hh:mm:ss). Based on 24-hour clock in GMT. * latitude: Measurement of location north or south of equator (decimal degrees). * longitude: Measurement of location east or west of prime meridian (decimal degrees). * sats: Number of satellites used to determine position of a fix. * HDOP: Indicator of GPS position quality (horizontal dilution of precision). #### File: nanotag\_phenology\_map.csv **Description:** This file contains radio transmitter (nanotag) tracking data from Common Terns breeding in western Lake Superior. Nanotags were only deployed at the Interstate Island colony in western Lake Superior. Sex (sex) and age class (age_class) are provided for each tagged bird (tag_ID). The columns (first) and (last) describe the date when a bird was first detected and last detected within one of the three defined stopover locations (region). The notes describe any locational data that were excluded from summaries. Nanotag data from this study were used to describe the southward phenology of Common Terns within the three defined regions by sex and age class. ##### Variables * tag_ID: Unique identification number associated with each radio transmitter (nanotag). This number was used to identify individual birds fitted with nanotags. * latitude: Measurement of location north or south of equator (decimal degrees). * longitude: Measurement of location east or west of prime meridian (decimal degrees). * age_class: Refers to age class of the bird fitted with a nanotag (Adult or Juvenile). * sex: The sex of each individual bird fitted with a nanotag. The sex of individuals fitted with nanotags was determined by blood sampling. Note that sex was not determined for all juvenile birds. F = female, M = male, and U = unknown. * region: Locations where nanotag tracking data were summarized. This includes Lake Erie, the Atlantic Coast, and Florida. * first: Date when a bird fitted with a nanotag was first detected within a specified stopover region (i.e. region). Format: mm/dd/yyyy. * last: Date when a bird fitted with a nanotag was last detected within a specified stopover region or at the breeding colony where it was tagged (i.e. region). Format: mm/dd/yyyy. * notes: Describes which data were excluded from summaries due to falling outside of specified autumn migration period (i.e. detections that occurred &gt; 1 yr post deployment. #### File: tag\_metadata.csv **Description:** This file contains detailed information regarding the deployment of tracking devices (tag_type) on Common Terns breeding at inland lakes in North America. For each bird, a unique identification is provided for the tracking device (tag_ID) and the leg band (band_number). Information as to where the bird was breeding at the time of deployment (lake and colony) and year of deployment (deployment_year) is provided, as well as the sex of the individual (sex), their corresponding age class (age_class) and family group (applicable only to birds fit with nanotags).  ##### Variables * tag_type: Refers to the type of tracking device deployed (geolocator, gps, nanotag). * lake: Location of the breeding colonies where Common Terns were fitted with tracking devices for this study. This includes only the name of the lake where the tags were deployed, not the specific colony name (Lake Winnipeg, Lake Superior, Lake Huron, and Oneida Lake). * tag_ID: Unique identification number associated with each tracking device. * band_number: Unique identification number of stainless steel leg band issued by the USGS Bird Banding Laboratory. * colony: Name of the breeding colonies where Common Terns were fitted with tracking devices for this study. This includes Egg Island on Lake Winnigeg, Interstate Island (Interstate) and Ashland Island (Ashland) on Lake Superior, Elm Island on Lake Huron, and Little Island on Oneida Lake. * deployment_year: The year (yyyy) in which tracking devices were deployed (2013 - 2020). * age_class: Age class of bird fitted with tracking device (Adult or Juvenile). * sex: The sex of each individual bird fitted with a tracking device. The sex of individuals fitted with tracking devices was determined by blood sampling or morphometrics. Note that sex was not determined for all juvenile birds. F = female, M = male, and U = unknown. * family: Refers to family group (i.e. adult nesting pairs and young). This information was only applicable to birds fit with nanotags. Family groups = M1 - M8. For birds not associated with any family group this column = "NA". ## Code/software There is no specific software needed to view this data. They are all .csv files. ## Access information Other publicly accessible locations of the data: * Solar geolocation data is available on Movebank ([https://www.movebank.org/cms/movebank-main](https://www.movebank.org/cms/movebank-main)) Data was derived from the following sources: * NA