BIMONTHLY BULLETIN of the CAYMAN ISLANDS DEPARTMENT of ENVIRONMENT ‘S TERRESTRIAL RESOURCES UNIT © Isabelle Brown WELCOME SOPHIE! Sophie O’Hehir has recently joined the Back at the office Sophie has been TRU thus replacing Jessica Harvey as digising long-standing data taken from one of the Department’s Terrestrial the Central Mangrove Wetland by Fred Research Officers. Burton in order to calculate volumes of carbon sequestering. This data Aes in Her main dues will consist of directly with the Terrestrial Protected undertaking the DoE’s biological Area Nominaons and offer a measure monitoring, assisAng visiAng scienAsts of the ecosystem services provided by with projects and execung TRU this nominated area. Addionally iniAaves. Sophie has been going through the drone footage taken for the Seabird project to idenAfy Brown Booby nests Coming originally from the UK with a along the bluff and the South Beach of Zoology degree from Swansea Cayman Brac. University, Sophie has worked in the UK, Costa Rica, and Ascension Island (part of the St. Helena Brish Overseas Sophie hopes to conAnue to meet lots Territory). Having previously worked of people interested in and involved with chariAes, NGO’s and the private with Cayman’s fauna and flora, so sector, Sophie is very excited to join the please feel free to introduce yourself if endeavours of the Cayman Islands’ you get the opportunity! Department of Environment. While having had hands-on experience with a wide variety of flora and fauna in both temperate and tropical environments, her most notable experience involves repAles, bats and marine turtles (including leatherback and green turtles). So far with the Department, she has been undertaking the biennial Cayman Brac Parrot survey and taken part in the Green Iguana control efforts on the Sister Islands with her colleague Jane Haakonsson. She has further assisted Dr Rhiannon Meier in the Darwin funded seabird project where she was involved in handling and tagging both Red-footed Boobies and Magnificent Frigate-birds in the Booby Sophie hanDling a Frigate-birD in the recent Pond Reserve. seabirD colony work on LiKle Cayman. Flicker Bulletin # 30 – MAY / JUNE 2017 TRU’s Biennial Bird Survey While the role of a conservaonist is Obtaining density or size esAmates for o]en diverse and complicated, most animal populaons can be problemac management of wildlife populaons and Ame consuming and even a single oen boils down to two relavely survey will do liale but give you an simple quesons: isolated snapshot in Ame, which is o]en of liale value. That is why long-term • How many animals do I have in monitoring programmes are in place the populaon? within well established conservaon organisaons around the world. • AnD is this number going up or down? The DoE has several monitoring programmes for both marine and These quesAons may seem simple, but terrestrial species of Cayman. Marine they are of utmost importance to assess species which are being rouAnely the trend of a wild animal populaon at monitored include the Queen Conch a given moment in Ame. Once obtained, (Strombus gigas), the Nassau Grouper this trend can be related to the various (Epinephelus striatus), sharks, corals and factors influencing the populaon turtles. Terrestrial species include the whether or not management acAons Blue Iguana (Cyclura lewisi), the Sister are performed. In other words, with Island Rock Iguana (Cyclura nubila baseline data it is possible to asses how, caymanensis), both Cayman Parrot for example, management or threats subspecies, seabird colonies and, for affect the abundance of individual example, the nave Inkberry (Scaevola animal species. plumieri). The White-Crowned Pigeon (Patagioenas leucocephala) is an indigenous species distributed throughout the Western Caribbean, the Central American Caribbean coastline anD the southern Pp of FloriDa. Flicker Bulletin # 30 – MAY / JUNE 2017 The TRU recently finished its biennial a seemingly thriving populaon may be bird survey which is carried out every more subjecve and vulnerable to other year on Grand Cayman and threats than first meets the eye. The Cayman Brac respecvely, in percentage of “floaters” may be as high cooperaon with the as 60 – 80% of the populaon. For US Fish and Wildlife Service. Originally example, in Cayman Brac the 2009 July started as the monitoring of both survey showed only around 25 breeding Cayman Parrot subspecies (the Grand pairs in a populaon of 291 (95% CI = Cayman Parrot and the Brac Parrot), this 203 to 417) birds. survey now includes several dove species, the Northern Mockingbird Studying populaons before and aer (Mimus polygloos), Vitelline Warbler external events, such as hurricanes, is (Setophaga vitellina) and the Red- equally important. Results give legged thrush (Turdus plumbeus). managers a picture of the resilience of a given populaon. Using again the Brac Surveys are carried out before (March) Parrot populaon as an example, and aer (July / August) reproducAon surveys showed 565 (95% CI = 409 to for the main focal species, i.e. the 782) birds in July 2008, before hurricane parrot, in order to establish the number Paloma and only 260 birds (95% CI = of breeding pairs. This is done because 199 to 441) aer Paloma in March 2009. parrots o]en have a high percentage of This number has been steadily non-breeding birds in the populaon increasing since, to 772 (95% CI = 603 to referred to as “floaters”, which is why 989) birds in July 2015 which subjecver suggestssuggest su The Cayman Brac Parrot (Amazona leucocephala hesterna) is an endemic subspecies of the Cuban Parrot, anD will, in me, evolve into its own full species on Cayman Brac. Flicker Bulletin # 30 – MAY / JUNE 2017 suggests an impressive but slow resilience through the use of density recovery from a single hurricane event. maps. These maps inform managers If, for example, two consecuve about increased aggregaon which is hurricanes were to hit Cayman Brac, we seen in most developed islands species. now know that with a populaon As available feeding and nesAng habitat decreased by around 50% (and thus very decreases (as direct results of few remaining breeding pairs) aer the development), endemics inhabit fewer first hurricane, this subspecies would areas in higher densiAes. This can be likely go exAnct aer the second. measured through “dispersion parameter b”, which assigns a randomly distributed species with a b-value of 1. Monitoring surveys can furthermore be Values above 1 shows increased used to assess factors influencing “clumping”. See below. resilience, such Species Before (b) Aer (b) Red-Legged Thrush 2008 = 3.38 2015 = 6.97 Brac Parrot 2008 = 1.11 2015 = 3.14 Grand Cayman Parrot 2005 = 1.68 2014 = 6.07 The table shows how 3 enDemic subspecies are increasingly being “pushed out” of suitable habitat. Cayman Brac Parrot density maps visually showing a comparison between the distribuons in 2010 and 2012. The dispersion parameter b is increasing and gives a numerical value to the aggregaon. 2017 data is pending analysis. Flicker Bulletin # 30 – MAY / JUNE 2017 While integrang monitoring efforts to To this end is important to remember inform management decisions may that certain populaons (like that of the seem obvious when protecAng a species WCP) cannot be considered such as the parrot, other bird species demographically closed populaons need to be monitored to inform take unlike, for example, the Cayman Parrot limits. These are our game-birds. populaons. alternavs The Naonal Conservaon Law outlines Seasonal and annual differences in the two current game-bird species of abundance may reflect births and the Cayman Islands, namely the Blue- deaths but also immigraon and winged teal (Anas discors) and the emigraon as WCPs can move between White-winged dove (Zenaida asia>ca). Grand Cayman, the Sister Islands, Take limits and seasons can only be set Jamaica and Cuba. Such fluctuaons are with an understanding of how mostly indirect results of varying levels populaons are currently doing and of rainfall and thus food abundance. The therefore how harvesng can be TRU is therefore keeping up to date with maintained sustainably. other Caribbean monitoring events of the species and collang rainfall data to get a beaer understanding of WCP For example, TRU has been monitoring migraons. the White-crowned pigeon (WCP) populaon on both Cayman Brac and For a full report on TRU’s bird surveys Grand Cayman since 2011 in and how results are used, please contact collaboraon with Dr. Frank Rivera- the editor, page 2. Milan from the U.S. Fish and Wildlife Service. When comparing the Grand Cayman density and populaon esAmates from 2011 to pre- and post- reproducve surveys in 2014, a significant decrease can be seen despite an unchanged detecAon probability. In 2011 we recorded 0.17 pigeons per ha in a study area of 15,550 ha (2,708 pigeons) which compared to 0.05 and 0.062 pigeons per ha (775 and 906 pigeons) in March and August 2014 respecvely, providing a significant decrease of almost 70%. As overhunAng is the primary threat for the WCP it has consequently been removed from the game-bird list according to the Naonal Conservaon Law. As the populaon monitoring White-winged dove (Zenaida asia6ca) conAnues, protecAon is carefully re- remains on the game-birD list unlike the evaluated and updated. White-crowned pigeon. Flicker Bulletin # 30 – MAY / JUNE 2017 Green Iguana Control on Cayman Brac Liale introducAon is needed when it strategy to prevent this highly invasive comes to the invasive nature of the species from geng a stronghold on Green Iguanas (Iguana iguana). They Liale Cayman and Cayman Brac as we are currently everything but a rare have seen it on Grand Cayman. sighAng around Grand Cayman and very few people need convincing that this With over 35 sighAngs of Green Iguanas species is bad news: from the keen on Liale Cayman since 2007 and many gardener, the pool owner, the naturalist more on Cayman Brac, it is clear that the to the average driver; green iguanas biosecurity between all three islands prove an overabundant nuisance.