RHWO History at CCESR 2017 – 2024
2024
The Red-headed Woodpecker Recovery (RhWR) became a non-profit corporation in May 2024. It was given the IRS Tax Exempt Status under Sec. 501(c)(3) on July 3, 2024. The RhWR can now accept tax exempt gifts and donations.
The RhWR volunteers continue to search for nesting activity at Cedar Creek Ecosystems Science Reserve (CCESR). After locating an active nest, Dr. Elena West’s field technicians verify eggs or young are present in the nest by taking photos using the nest hole camera.
The Roost Biology Study is continuing at CCESR. Again, partly funded by the RhWR. Some nest port holes are being made by RhWR volunteers to be able to capture nestlings so they can be color banded and fitted with a radio transmitter for this study. Some adults are also being caught, color banded and fitted with a radio transmitter for the study.
The nest cams are still in place taking candid videos of everything that moves in front of them. These videos are prepared for viewing on the Zooniverse website to assist our researchers in paring down the very large number of videos for more intense scrutiny. This continues to provide new information about the RHWO and the other creatures that interact with them.
The breeding bird surveys conducted by RhWR volunteers has completed its second year documenting birds and some other animals at CCESR.
2023
Dr. Elena West is beginning a Red-headed Woodpecker (RHWO) Roost Biology Study partly funded by the RhWR. Dr. West and field technicians are placing radio transmitters on both adults and nestlings so that they can determine where they roost for the night. RhWR volunteers assist this program by helping to identify nest sites. This helps identify potential nest trees that nest portals can safely be put into and allows the field technicians to capture the nestling before it fledges so that they can be color banded and fitted with radio transmitters.
The RHWO Bioacoustics’ study is in its second year with RhWR funded field technicians placing acoustic recording units (ARUs) at randomly selected public locations around Minnesota to make recordings of sounds that a computer analysis can determine if there are RHWOs calling in the area, thereby being able to get a count of birds in an area and using statistical technique be able to get an accurate estimate of the RHWO population in Minnesota.
An acorn survey has been conducted at CCESR for the last six years with this year’s crop being the largest to date. This indicated to us that the RHWOs would not leave for the winter and they did not. Read the article in the Fall 2023 The REDHEAD.
2022
Dr. West described her upcoming research in the Fall 2021 The REDHEAD.
This will be the first year of the Bioacoustics Study that will be funded by a grant from the Legislative and Citizen Commission on Minnesota Resources (LCCMR). The RhWR will provide some funding to assist this study. This year will involve recording Red-headed Woodpecker (RHWO) calls and using them to prepare algorithms to be used to identify RHWO calls amongst the sounds recorded by the acoustic recording units (ARUs). The Summer 2022 The REDHEAD features an article describing the calls and their spectrograms.
Red-headed Woodpecker Recovery (RhWR) volunteers (18) have completed three Breeding Bird Surveys at Cedar Creek Ecosystem Science Reserve (CCESR) on 13 one-kilometer long transects with 5 count points on each transect. This was the first year of the survey and they are expected to continue each coming year. The CCESR administration requested that the RhWR conduct these surveys to document the many different bird species found at CCESR.
Eight nest cams will again be taking short videos of activity at the nest holes. If we add the hours of observation time that these nest cameras have added since last fall, the cameras will have logged over 125,000 hours at RHWO nests since they were started in late 2019. The data collected so far has documented behaviors and activities at these nest cavities that is new and exciting and in extensive detail.
2021
Trail cameras at Cedar Creek reveal new animals and behaviors
Dr. West and her team have trail cameras at active and non-active nests again this summer, which are continuing to yield exciting new behaviors not seen before and some surprising life and death encounters. Most RHWO nests are in dead or dying trees, including a few that one can hardly believe are still standing. During a strong windstorm in the early morning hours of June 24th, an active nest tree was blown down and broken apart. Miraculously, the two nestlings inside were not injured, the cavity was not damaged and landed with the hole facing up. Surprisingly, the nest camera was also not damaged and continued to collect images. By sunrise, the parents were at the nest cavity, now on the ground, looking into the nest hole, making concerned
calls. By 6:15 am the trail camera recorded them bringing food to the nestlings (see picture of adult at the cavity on the ground) who maintained their loud calls for food after the fall. At 12:27 pm, two members of the research team discovered the nest on the ground and with quick thinking, dug a hole in the ground nearby and “re-planted” the section of the tree that had the nest cavity in it. The adult woodpeckers were recorded at the cavity feeding the nestlings within minutes of the researchers leaving. What’s particularly interesting about this event is that the trail camera captured how the parents at this nest continued to attend to their nestlings, despite it being on the ground.
Unfortunately, the journey of this nest did not end well, as a large Bull Snake made its way up the tree on July 2 and ate the two nestlings inside.
This nest had also previously survived a predation attempt by a Fisher (see below for details), but unlike this large mammal, the snake was able to get inside the cavity. The replanted tree was only 5-6 feet high, and may have been low enough for the snake to smell the nestlings and access them. Bull snakes are one of the very few successful nest predators of RHWOs that the researchers have documented so far.
Before this nest blew down and met its end by the Bull snake, it also had an encounter with a Fisher, which was the first time our research team has captured one on video. Fishers are uncommon in the Twin Cities
metropolitan area, but are seen more regularly in the north metro and the area around Cedar Creek Ecosystem Science Reserve (Cedar Creek). There were three nestlings in the nest on June 16th when a Fisher was captured by the trail camera at the cavity entrance trying to get at the nestlings. The Fisher put its nose into the cavity and could likely smell the nestlings inside. The shape of the nest cavity excavated by the parents —narrow at the top and deep — foiled the Fisher and it went away empty handed, or with empty paws.
In addition to recording the daily happenings at active nests, some of the research team’s cameras are also continuing to record videos of what goes on at nests that are no longer thought to be in use by RHWO. After reviewing some of the videos captured this year, the research team learned that a camera left at a previously used cavity (2020) had captured the same pair using it again this year as a “secondary” cavity. The pair had returned to Cedar Creek this spring and nested in a different hole about 120 feet from their 2020 tree. The camera recorded them at the old cavity only a few times in 2021 until they started showing up fairly regularly in late June. On July 7th, one of the pair’s very new fledglings was recorded inside the cavity at about 8:45 pm with both parents present. Over the next six days both adults and 2-3 fledglings are recorded on over 200 different occasions. It appears to be quite a family affair as sometimes up to four members of the family are present in videos at one time. There are many videos of the parents feeding the fledglings, of sibling fights and attempts at dominance. One fledgling can be seen inside the cavity (possibly roosting there at night). This is new and exciting behavior to document and demonstrates the importance of previously used trees for RHWO across multiple years.
Siah St. Clair
Potential RHWO Nest Cavity Use by Other Bird Species in Spring 2021
On April 22, 2021, three RHWO nest cameras that had been left out through the winter at Cedar Creek ESR had their memory cards replaced and batteries checked to prepare for the returning RHWOs this spring. When looking at the memory cards that were removed it became obvious that a few bird pairs were considering or definitely preparing to use an old RHWO nest cavity for their own nests this spring. Returning RHWO pairs may dispute cavity ownership, and may or may not win back their cavity if they choose to fight for it.
Nesting pair interests documented by the RHWO nest cameras this spring include:
1. A Pileated Woodpecker pair took an interest in the cavity at nest tree 84. The camera captured them 12 separate times at the nest since November 3, and as a pair present together at least 3 times. On March 22 they “talked” softly together while checking out the nest. Unfortunately, a wind storm blew the huge dead nest tree 84 down on March 24. So ended the exciting possibility of recording a Pileated Woodpecker pair nesting from beginning to completion in a former RHWO nest cavity.
2. On March 18th, a pair of Bluebirds were captured by the camera at nest 223. Both the male and female were going in and out of the cavity calling to each other. The camera recorded 61 events with this pair of Bluebirds removing old nest material from inside the cavity, talking and calling to each other, both going in and out of the cavity. Unfortunately, a pair of European Starlings also discovered the nest, and the Bluebirds finally stopped showing up on April 3.
3. On March 18th a pair of European Starlings also discovered the nest cavity at nest 223. The camera captured 83 events with Starlings at the cavity between March 18 and April 20. The camera captured a fight with an intruding 3rd Starling, Starlings removing mouthfuls of nest debris 29 times, and many interactions between the pair. There appears to be a good chance that this pair may nest at this site unless driven away by an aggressive pair of returning RHWOs.
As ecosystem engineers, Red Headed Woodpeckers create cavities that other species use or adapt for nests, roosts, and other purposes. RHWOs are important for the survival and reproductive success of other species within their ecosystem.
by Siah St. Clair
2020
Tracking Data Reveals Red-headed Woodpecker Migration Route
By Dr. Elena West, University of Minnesota, Lead RHWO Researcher
Red-headed Woodpeckers are facultative migrants, meaning that they leave their breeding grounds during some winters but not during others. In general, facultative migration occurs in populations that experience seasonally fluctuating, but year-round, food at breeding sites, but it can occur due to other factors such as weather events. In contrast to facultative migrants, obligate migrants tend to leave breeding sites at the same time, in the same direction, and to the same wintering areas each year. The seasonal movements of facultative migrants are not well understood due to their irregular and often unpredictable occurrence.
Our understanding of the migratory movements of Red-headed Woodpeckers is limited to mostly anecdotal accounts and has focused on variation in food resources (i.e., annual mast production) as the primary factor hypothesized to drive whether individuals or populations leave their breeding sites in autumn. Determining the timing and distance of migratory movements, and sites used by Red-headed Woodpeckers outside of the breeding season are important for understanding their population dynamics, informing annual cycle conservation plans, and identifying the cues that may drive their migration patterns.
Over the last three breeding seasons at Cedar Creek Ecosystem Science Reserve (Cedar Creek), we have marked 50 adult Red-headed Woodpeckers with miniature GPS tags to track autumn and winter movements and to better understand the frequency, timing, routes, and overwintering locations of birds that migrate from Cedar Creek. Prior to marking birds with these GPS tags, we programmed GPS tags to record location estimates, once per week during the summer and winter months (May-August, December-February) and once every three days during the months in which we expected migration might occur (September-November, March-April). Each spring we attempt to recapture birds wearing these devices so that we can remove them (which are attached using harnesses made with strong ribbon) and download the stored data that shows where birds spent the non-breeding season.
Until recently, all of the data showed that the birds we recovered devices from spent their winters in and around Cedar Creek. However, in June 2019 we recaptured a female Red-headed Woodpecker that had been marked with a GPS tag in 2018, migrated to southeast Iowa in the fall, and returned to Cedar Creek sometime in 2019. The data from this bird’s device indicates that she left Cedar Creek between September 1 – 4, 2018 and arrived in southeast Iowa sometime between September 7 – 10, where she appears to have spent the fall and early winter. During this bird’s journey south, the device recorded a location on September 4 a few miles west of Wyalusing State Park, along the Mississippi River. On September 7, the device recorded a location a few miles outside of Dubuque, IA. Both of these locations appear to be in small, dense forest patches within landscapes dominated by agricultural fields.
Location data from the device indicate that this bird spent the next three months in the southeast corner of Iowa, near the borders of Illinois and Missouri, in a patch of dense forest a few miles from the Mississippi River. Battery life on this device was shorter than expected and it stopped collecting data after December 27, 2018. Presumably this bird spent the remainder of the winter in this area, then returned to Cedar Creek in the spring. While the map shows known locations taken during the bird’s fall migration, the lines connecting these points are not representative of the bird’s path—birds do not fly entirely straight during migration after all! Based on the proximity of the points to the Mississippi River, it seems likely that the bird traveled along the Mississippi River flyway from Minnesota to southern Iowa. Our hope is that over the next two years we are able to recover more GPS tags from red-headed woodpeckers that migrate from Cedar Creek so that we can learn more about the species’ migration patterns and inform conservation planning throughout its range.
2020 Research Team
Introducing the 2020 Red-headed Woodpecker Research Team. The Team is again led by Dr. Elena West, who is starting her fourth year leading the red-headed woodpecker research.
We are very happy to have April Strzelczyk back for a second year. April is from Carol Stream, IL and received her Bachelor of Science degree in Biology from Bemidji State University in 2013. Since then, she has developed a passion for researching human impacts on wildlife populations. April has worked on a range of research projects and has developed wildlife surveys and volunteer programs to promote a better understanding of wildlife in regional parks. Some of her past projects include: distance sampling and mortality rates of white-tailed deer, avian influenza in waterfowl, bird-building collisions, road mortality, and presence surveys of marshbirds, small mammals, fisher, bats, bumblebees, snakes, turtles, and frogs. April in her second season with the Red-headed Woodpecker Recovery is looking forward to learning more about these amazing birds.
April Strzelczyk
Kirsti Carr has joined the Team this year. Kirsti grew up in Connecticut and received a Bachelor of Science degree in Wildlife and Fisheries Biology from the University of Vermont in 2018. She wrote her undergraduate thesis about the basking behavior of Spiny Softshell turtles and also assisted with researching the song structure of southern hemisphere humpback whales. Since then, most of her field work has been with birds, her truest passion, including monitoring Common Loon populations in Vermont and montane songbird surveys throughout New England. Most recently she has worked in California and Nevada, counting and banding raptors in fall migration. She has also worked on nesting studies of Swainson’s Hawks, Osprey, and Barn Owls. She’s an avid birder and is fascinated by breeding ecology and molt in birds and has loved working on the Red-headed Woodpecker team thus far.
Kirsti Carr
Kirsti Carr, Dr.Jim Howitz, April Strzelczyk, Dr. Elena West
2020 Research Results
Dr. Jim Howitz, RhWR Research Team and Dr. Elena West, University of Minnesota, Lead RHWO Researcher
The 2020 red-headed Woodpecker (RHWO) field season at the Cedar Creek Ecosystem Science Reserve (Cedar Creek) ended in September and despite a number of constraints due to the Coronavirus pandemic, it was a very productive season. A large number of RHWO that overwintered at Cedar Creek this past winter also nested on site, so we (the research team) were able to hit the ground running in early May to begin nest monitoring, recapturing birds that were marked with GPS devices in 2019, and marking a new sample of birds with tracking devices. We were lucky to have two extraordinary field technicians, April Strzelczyk (joining us for a second year) and Kirsti Carr. Some highlights of our field work include:
- 57 RHWO nest trees monitored and a total of 68 nest attempts (first and second attempts combined)
- 45 of the nests we monitored successfully fledged at least one bird.
- Most first nests had fledglings by the end of June while fledging stretched into August and early September for second nest attempts.
- We marked 24 adult RHWO with GPS devices—nearly all of which appear to have left Cedar Creek for the winter, which may be due to the lower than usual acorn count. The fact that so many adults appear to have migrated this year is an exciting prospect for their return to Cedar Creek in the spring when we hope to recapture these birds to retrieve their movement data.
Another highlight of the 2020 field season is the installation of 9 nest cameras that have revealed some very interesting findings about how RHWO and other animals use cavities. These cameras will continue to take videos of nest cavities during the fall, winter, and spring. We are working to develop a project accessible to the public so that volunteers can help classify the behaviors captured in these videos. Our hope is that the cameras will record additional information on the presence and activities of other animal species that use RHWO nest cavities throughout the year. Stay tuned.
We also completed a project to measure RHWO nest tree density; the results of which will help us understand the role of wood hardness in nest site selection and in limiting nesting opportunities. Ultimately, this information will be used to guide land managers and private landowners working on red-headed woodpecker habitat restoration efforts around the state.
We hope to be able to continue field work in spring 2021 as we move onto the next phase of our research.
2019 Research Team
By Jerry Bahls, RhWR Communications
The Red-headed Woodpecker Recovery (RhWR) 2019 research team has again been assembled with three talented researchers. The team is again headed by Dr. Elena West and assisted by Ornithological Research Technicians April Strzelczyk and Sarah Stewart. Below are biographies of this outstanding team.
Dr. Elena West, University of Minnesota Research Associate, is an avian ecologist and conservation biologist with broad research and teaching interests in animal foraging and movement behavior, and quantitative wildlife population ecology. Dr. West was contracted by the Red-headed Woodpecker Recovery (Audubon Chapter of Minneapolis) in 2017. She has just completed a postdoctoral research position in June with Dr. Henry Streby at the University of Toledo and Audubon Chapter of Minneapolis directing the Red-headed Woodpecker (RHWO) research. She completed her M.S. in Natural Resource Ecology and Management at the University of Michigan where she also received a graduate certificate in GIS and Spatial Analysis. She completed her PhD in Integrative Biology (formerly Zoology) at the University of Wisconsin-Madison where she examined the influence of anthropogenic food subsidies on the behavior and ecology of Steller’s jays in California state parks. In her current position she is examining the annual cycle demography, habitat associations, and migration ecology of RHWOs in Minnesota.
April Strzelczyk is from Carol Stream, IL and received her Bachelor of Science degree in Biology from Bemidji State University in 2013. Since then, she has conducted research on avian, mammalian, reptilian, and insect species. April has worked on a range of projects from assessing bird-building collisions, avian influenza in waterfowl, abundance and distribution of sharp-tailed grouse and wild turkey, population demographics of Blanding’s turtles, population density of bumblebees, and mortality investigations in white-tailed deer. April has also developed wildlife surveys and volunteer programs to promote a better understanding of wildlife in regional parks, through her work with Dakota County Parks. She has a broad range of research interests and plans to continue working on projects that involve human impacts on wildlife populations.
Sarah Stewart is from Charleston, South Carolina and received her Bachelor of Science degree in Wildlife and Fisheries Biology from Clemson University in May 2019. Her previous field experiences with threatened red-cockaded woodpeckers (Dryobates borealis) sparked her interest in the ecology of cavity nesters and their impacts on forest communities, particularly those that are fire-dependent. Her work with red-cockaded woodpeckers involved monitoring active nest cavities, collecting and banding nestlings, and estimating fledgling survival by re-sighting color band combinations at nest clusters. During the summer of 2018 Sarah worked on a research project assessing the demography and health status of common map turtles (Graptemys geographica) in the oil-polluted Kalamazoo River, Michigan. Her time on the Red-headed Woodpecker Recovery has already provided her with many rich field experiences, and she looks forward to continuing her work in avian conservation and research after this season ends.
2018 Field Season
Dr. Elena West, University of Minnesota, Lead RHWO Researcher
The 2018 Red-headed Woodpecker field season came fast and furious with a record setting mid-April snowfall and an early start to courtship and nesting by many of the birds at Cedar Creek Ecosystem Science Reserve (Cedar Creek). Red-headed Woodpeckers paid no mind to the cold and snowy conditions and started their breeding season activities approximately 3 weeks before last year’s breeding season. One of our most enthusiastic and skilled volunteer photographers, Siah St. Clair, was able to capture a number of Red-headed Woodpeckers actively foraging for insects on tiny leaves that had just emerged amidst the snow-covered trees. We suspect that the early start to breeding was a result of so many woodpeckers overwintering at Cedar Creek, allowing them ample time for courtship and cavity excavation during the spring.
Much of our research is made possible with the assistance of our citizen science volunteers who conduct surveys throughout Cedar Creek’s oak savannas to identify potential red-headed woodpecker nest sites. Volunteers identify these sites by observing woodpecker behaviors, including courtship displays, movements in and out of cavities, defensive displays, and cavity excavation. From May until August, over 40 citizen scientists conducted nearly 75 surveys, totaling more than 160 hours. Many volunteers also spent additional time photographing Red-headed Woodpeckers and their interactions with other bird species. We have over 19,000(!) photos, which is an incredible repository of information for the project.
Much of our work early in the field season is made up of daily nest checks. Once volunteers on the project locate potentially active Red-headed Woodpecker nests, members of the research team confirm whether the nest is active by hoisting one of our telescoping measuring poles toward the nest cavity, inserting the attached camera, and taking a look. This year we were able to monitor 44 nest trees and we noted at least three additional trees where nesting took place, but we were unable to monitor them because we could not access the cavity due to its height or entrance hole diameter. A total of 24 nests fledged at least one juvenile during first nest attempts, while 11 first nesting attempts failed. Of these 11 nests that failed, we were able to confirm that four were due to predation and one was caused by a tree blow down. We were unable to determine the cause of failure for the remaining six nests.
GPS Pinpoint
Radio Transmitter
We were pleasantly surprised to find that a number of pairs nested a second time this summer. We observed a total of 20 second nesting attempts, 12 of which fledged at least one juvenile and eight of which were unsuccessful. While we were able to confirm that three of these eight failures were caused by predation events, we were unable to determine the cause of failure for the remaining five nests. The challenge in these cases is that nests are found empty, and without visible evidence of a predation event or carcass(s) present, it’s difficult to determine the cause of failure.
In addition to nest monitoring, one of our major tasks this summer was to recapture as many of the adult woodpeckers we marked with pinpoint GPS units during the 2017 breeding season. We were able to retrieve five GPS units (out of 20) and we’re hopeful that we will be able to recover additional units over the next few breeding seasons, including the 12 that we attached to birds this summer. Data from the GPS devices will provide information on whether birds migrated or overwintered at Cedar Creek. Attached to each GPS device is a geolocator, which measures light-level data, which will provide information on cavity use and incubation.
Much of the field work this summer was also spent tracking individual adults and juveniles that had been marked with radio-transmitters. We tracked 16 adults to collect habitat use and home range data, including territory size and overlap. We marked 18 nestlings with radio-transmitters prior to fledging in order to track their daily movements, habitat use, and post-fledging survival. We also collected tissue samples from each captured bird, which we will compare to prey samples using stable isotope analysis as part of our study to determine woodpecker diets. Stable isotopes are a useful tool for reconstructing consumer diets as the isotopic ratios of nitrogen (15N/14N, noted δ15N) and carbon (13C/12C, noted δ13C) in consumer tissues predictably reflect those in their diets.
By the end of September, we were unable to locate most of the birds we had marked with radio-transmitters. Many adults appear to have migrated (adults) or made first-year dispersal movements (juveniles). As the field season ended, the most dramatic moments seemed a distant memory. A huge highlight from the season include was our determination that two “trios” of birds were exhibiting polyandry, which is the first time this behavior has been described in this species (more to come on this story this fall and winter!).
Data analysis is in full swing and will be ongoing throughout the duration of our multi-year study. We look forward to sharing preliminary results in the coming months and planning for another action-packed field season. A huge thank you to all of our fantastic volunteers for their interest, support, and dedication to Red-headed Woodpecker research and recovery! Be sure to follow our blog for updates and photos from the field season and on our future work: www.rhworesearch.org [Editor note: Blog has been discontinued]
2017 Cedar Creek Research Update
By Jesse Beck and Candace Stenzel, RhWR Ornithological Research Technicians
The Red-headed Woodpecker Recovery project 2017 breeding season is soon coming to an end. Our project goals for this season have been to 1) find and monitor active Red-headed Woodpecker nests, 2) build port holes to extract nestlings from nest cavities, 3) capture adults and nestlings for banding, body measurements, blood sampling, and attachment of geolocator backpacks, 4) track backpacked fledgling movement using radio telemetry, and 5) recapture backpacked adults to retrieve movement data from geolocator chips.
While the first 3 goals were more heavily focused on throughout the first half of the season, our efforts shifted more on the last 2 goals during August and September.
To quickly recap the numbers for this season, we have so far captured 66 individual birds, with 50 being adults and 16 being hatch-years. We attached geolocator backpacks on the first 20 adults, and radio-transmitter backpacks on 15 of the 16 hatch-years. After attaching the radio-transmitter units, we have been going out at least 3 to 4 times a week to track hatch-year movements and habitat use post-fledge. We are currently tracking only 4 of these 15 birds. For the 11 other birds, 3 were confirmed as being predated (we found piles of feathers surrounding the transmitter units), 2 of the backpacks fell off post-fledge, which no longer allowed us to track, and 6 birds mysteriously went missing (we haven’t been able to pick up any signals on the receivers we use for tracking).
Goal 5, recapturing the geolocator backpacked adults, has proven to be a larger challenge than we originally expected. Earlier in the summer, we were effectively using potter traps baited with peanuts for trapping birds. We assumed that this method would be just as effective when recaptures started in August. However, once we began the recapture attempts, the birds seemed to have lost all interest in the peanuts and no longer fly into the traps. Thus, we switched to using mist nets for recapture efforts, which has been working out better, but we still have only captured 8 of the 20 backpacked adults. We think that some of the birds may have already begun migration, or shifted to a different area, for we haven’t been able to find them for quite some time. However, we still have another 2 weeks left of the research season and hope to capture at least 2-4 more. For the 8 birds that we have recaptured, we have been hooking their backpack units up to a laptop to obtain movement data, and then transferring the data onto GIS for spatial analyses. We hope that come springtime; the project will be able to recover the additional birds that we were not able to capture this season.
While we are sad that this research season is soon coming to an end, we are nonetheless pleased to have been a part of such an incredible project. We greatly appreciate all of the support and encouragement everyone has given us, and we hope that we have effectively laid out the groundwork for all future efforts.