Common Whitetail Plathemis lydia, sometimes called "White-tailed Skimmer," was not "officially" added to the Monterey County checklist until 2006 despite a long and rich history of studies within the county. The history of these events is laced with irony and serendipity, and they are laid out below.

Our story begins at Hastings Natural History Reservation in upper Carmel Valley. It was established in October 1937 as a field research station for the Museum of Vertebrate Zoology at U.C. Berkeley. The habitat here includes much rolling oak savanna (as shown in the header photo, above). Jean M. Linsdale of the Museum staff became the first resident director. Natural history studies included a wide variety of subject, although much emphasis was placed on birds. Jean's son, Don Linsdale, was interested in the insects and between 1938-1943 a collection of insects developed, including 15 species of Odonata (now housed at the Oakland Museum). Plathemis lydia was not among them. The small stock pond on adjacent land — to be called "Blompond" in research papers (see below) — was not yet present (it was created ~1970). Since Common Whitetail is primarily a pond species, it was likely scarce at Hastings during the Linsdale era.

In the mid 1970s, Walt Koenig began longterm studies of Acorn Woodpeckers at Hastings NHR. He would acquire his PhD at U.C. Berkeley and become the resident research scientist at Hastings for the next two-and-a-half decades. In summer 1982, Koenig began to consider the feasibility of research studies on dragonflies at "Blompond", a small man-made stock pond located in oak savannah on a ranch adjacent to Hastings NHR (that's Walt, right, standing in Blompond in summer 1982). In summer 1983, Koenig and grad student Stephen Albano undertook a study of the behavior ecology of Common Whitetail on Blompond , and several other more distant stock ponds. They captured 301 male and 78 females for a study of territoriality and mating success (Koenig & Albano 1985). In summer 1984, Koenig, Albano, and research associates captured and marked 180 males and 84 females for a studies on lifetime reproductive success, selection, and site fidelity; 66 of those marked were transplanted to Blompond for the latter project (Koenig & Albano 1987a, 1987b). In summer 1985, Koenig captured and marked 48 more males in a study on territory size and duration. Near the bottom of this page, I summarize some of the findings of the Hastings studies.

Below are a couple of photos from the research project in summer 1984. There's a shot of Steve Albano at his "look-out" station on the pond, and then a group shot of the researchers (Steve, assistants Monica and Adam, and Walt on the far right; all photos from 1982-1984 © W.D. Koenig):

In all, Hastings researchers captured 691 Common Whitetails over 3 summers; marked them with small colored dots (see photo, left), and released them to observe their behavior and ecology. It is fair to say that no one in California knew Common Whitetail better than Walt Koenig and colleagues.

A decade later, in the late 1990s, the first attempts to create standardized state and county checklists for Odonata got underway. The criteria developed for these lists at first required specimens but eventually included good photographs. As Koeing and colleagues took no specimens, nor placed any photographs in museums or publications, their work was overlooked in creating the checklists. Thus it happened that when Rita and I (Don Roberson) became interested in odes — 23 years after the first Hastings study — Common Whitetail was not included on the Monterey County ode checklist! When I first learned this in late July 2006, I was puzzled but, as I learned more of the history, the irony of it all grew more and more amusing.

Walt Koenig scanned this photo (left) for me in November 2006, long after the "rest of the story" that follows. In retrospect, it is the first Monterey County photo of P. lydia. For purposes of our story, however, this photograph was not known to exist.

On 9 June 2006, Paul Johnson was among those participating in the annual Summer Butterfly Count at Hastings NHR. During the count he observed several interesting butterflies, but also found and photographed 3 different Common Whitetails in the Hastings vicinity. These were a young male (below left) and two females (below, right-hand two). These are apparently the first photos for MTY, but Paul did not know at the time the species was "unrecorded" in the county, so they were not submitted to Odonata Central for inclusion on the "official" list.
photos (above) 9 June 2006 Hastings NHR © P.G. Johnson
photo (below) © W. D. Koenig; all used with permission
On 1 July 2006, Rita Carratello & I visited Hastings NHR to look at a roost of bats in Walt Koenig's garage. Afterwards, sipping ice tea on Walt's deck, we happened to mention a budding interest in dragonflies. Walt told us about his research on Common Whitetail. He and grad student Justyn Stahl (photo right; Walt is in the blue hat) took us over to Blompond to observe them. We saw several Common Whitetails and even watched a female ovipositing in the pond while the male hovered just above her. We also did not then know that the species was "unrecorded" in MTY (we did not even know there was a Monterey ode checklist at the time), and so we didn't report these observations.
Steve Rovell did know that Common Whitetail was not on the "official" county checklist, as he had been odeing in MTY for a couple of years. On 13 July 2006, he found this male (left) on Lake Lagunitas, a small drainage lake in rolling grasslands northeast of Salinas and now converted to a stock pond on private land. Steve reported the find to CalOdes and sent it through Odonata Central. This is considered the first "official" record for Monterey County. Steve had 2 males and 2 females here.

photo © Steve Rovell, used with permission

Between 24 July-10 August, I located Common Whitetails at four additional sites in MTY. Up to 4 males were patrolling territories on Arroyo Seco Lakes on 24 July 2006 (one of them is shown above). It is interesting that there are no prior records from this area, despite the fact that the Arroyo Seco Campground area was surveyed for odes on at least these dates: 14 May 1972, 18 Aug 1973, 27 May 1974, 19 July 2004, and 1 July 2005. Perhaps there are 'good' years and 'bad' years for whitetails in MTY, and the flight season may be rather short. Indeed, on a return visit on 5 Aug 2006, we found none.

On 24 July 2006, I found a male (photo left) in Laguna Grande Park, Seaside, less than a mile from the coast. All other known locales have been in the hot, humid interior of the county.

In the studies at Hastings NHR, very few tenerals emerged from Blompond. The evidence gathered there suggested that almost all the breeders on Blompond came as dispersers from elsewhere (Koenig & Albano 1987). There are apparently widespread local movements in this species.

Common Whitetail is a widespread and familiar species across North America. Its absence from the MTY checklist until 2006, as described above, is just an ironic oversight. The map (right) shows the locales at which it was observed in 2006. It probably occurs at many interior lakes, tule-lined ponds, and stock ponds.

In studies at Hastings NHR in upper Carmel Valley, breeding activity was limited to the 11-12 weeks between mid-May and early August (Koenig & Albano 1985, 1987a, 1987b. The latest MTY record is just 10 Aug 2006 on a stock pond near Soledad (D. Roberson). Elsewhere in California, flight dates range from March-October. Its (apparently) short flight season in MTY is somewhat of a mystery.

Short Summary of Research Findings at Hastings NHR

Koenig & Albano (1985) marked and watched the behavior of 301 males and 78 females (379 in all) between 15 June-31 July 1983. Males defend a territory of ~10m long around the perimeter of the pond. Females comes to the pond only to mate, and generally arrive about the same time in early afternoon. They oviposit immediately after mating by dipping their abdomen into the water while the male 'guards' her by hovering overhead (to avoid matings by other males). Females leave the pond immediately after ovipositing (the eggs develop unattended). Only 79% of males known to be alive visited the pond on any particular day. Those that came were divided between territorial males and non-territorial 'poachers,' but the same individual could have both behaviors on the same day. Males never tolerated males within their territories but always chased interlopers. When densities are high, males spend only a few hours each day to the pond, so each territory is defended by a series of males each day (up to 7 males may defend the same territory sequentially). Individual males tended to return to the pond at the same time each day, thus "time-sharing" the few available territories. 

Koenig & Albano (1987a) marked and watched the behavior of 180 males and 84 females (264 in all) in the latter half of the breeding season. In the study, females came to the pond every 1-5 days they were alive. The researchers measured lifetime reproductive success and the effects of selection, presented in substantial and innovative statistical detail. In this study, and the preceding and following study, the researchers essentially captured the entire summer population on Blompond.
    Adults do not overwinter. They live rather short lives as adults. The 'average' male lived only ~9 days when breeding at the pond, the 'average' female only 6 days. Day-to-day lifetime survivorship is 83-89%. It appears that the longest lived whitetails may be present for up to 3 weeks.

Koenig & Albano (1987b) watched 122 residents at Blompond (91 male & 31 female) and 66 transported to Blompond from other ponds (57 male, 9 female) to determine their site fidelity. The study took place between 19 June-5 Aug 1984. Of the 122 residents from Blompond, 25% were never seen again (natural mortality, stress of handling, or dispersal). 75% were seen again at Blompond but 12% (all males) dispersed to other ponds. Of those transported to Blompond from elsewhere, 57% remained there but 15% went back to their original ponds. The longest stay by a transplant at Blompond was 18 days. Those breeding adults that were being successful in matings stayed at Blompond. Post-breeding dispersal late in life did not lead to significant new matings.

Koenig (1990) marked 48 males between 29 June-31 July 1985 and watched their behavior. Males were at Blompond between 1-24 days; 452 matings were noted. Males with larger territories had greater breeding success and lived longer.

Common Whitetail is a fat-bodied, rather large skimmer. Males have distinctly patterned wings, and full adult males develop much white pruinescence on the abdomen.
photos of males (above) 19 June 2006 Hayfork, Trinity Co., CA © D. Roberson
photos of female & young male (below) 12 Aug 2006 American River Parkway, Sacramento © D. Roberson
Females (below) have differently patterned wings and a brown body with distinct white dashes on the sides of the abdomen [see Manolis 2003 for separation from other skimmers].
Immature males have female-like bodies but male-patterned wings (below).
Many thanks to Walt Koenig, Paul Johnson, and Steve Rovell for providing their photos, and for commenting on draft of this web page.
Literature cited:
  • Koenig, W.D., and S.S. Albano. 1985. Patterns of territoriality and mating success in the White-tailed Skimmer Plathemis lydia (Odonata: Anisoptera). Amer. Midland Naturalist 114: 1-12.
  • Koenig, W.D., and S.S. Albano. 1987a. Lifetime reproductive success, selection, and the opportunity for selection in the White-tailed Skimmer Plathemis lydia (Odonata: Libellulidae). Evolution 41: 22-36.
  • Koenig, W.D., and S.S. Albano. 1987b. Breeding site fidelity in Plathemis lydia (Drury) [Anisoptera: Libellulidae]. Odonatologica 16: 249-259.
  • Koenig, W.D. 1990. Territory size and duration in the White-tailed Skimmer Plathemis lydia (Odonata: Libellulidae). J. Animal Ecol. 59: 317-333.
  • Manolis, T. 2003. Dragonflies and Damselflies of California. Univ. of Calif. Press, Berkeley.
Web resources:
Major identification web sites with much information on California odes include: For sites with excellent photos to compare for identification or to simply enjoy, see: Many of these sites have links to other useful pages. Kathy Biggs's site is particularly useful in her selection of links.

Photos © Don Roberson 2007 or copyrighted to the photographer credited, and used with permission; all rights reserved


Page created 2-3 Nov 2006