National Survey of Red-billed Gull, 2014-2016

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Peter Frost
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National Survey of Red-billed Gull, 2014-2016

Postby Peter Frost » Sun Oct 05, 2014 12:13 pm

What is the current status of red-billed gull (Larus novaehollandiae scopulinus) in New Zealand? In the mid-1960s, Lou Gurr and Fred Kinsky pulled together all known information on the distribution and size of red-billed gull colonies nationally, extending as far back as 1889 (Gurr and Kinsky, 1965). They identified 166 sites on the main islands of New Zealand and those offshore (i.e. excluding the Chathams and sub-Antarctic Is, where at least 13 other sites were noted), and estimated an overall population of around 40,000 pairs (see the attached figure; click on it if it doesn't show fully first time).

Distribution_colonies_mid1960s_for BirdingNZ-net.jpg
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More recently, Jim Mills, the leading authority on red-billed gulls, has reported marked declines in the numbers of birds breeding in the largest colonies -Three Kings and Mokohinau Is, and at Kaikoura - over the past 20 years (Mills, 2013). Conversely, Lyndon Perriman and Chris Lalas report increases of 6–10% over the same period along the Otago coastline (Perriman and Lalas, 2012). The Department of Conservation categorises the species as Nationally Vulnerable, based on a predicted decline of 50–70% over three generations despite an apparently large population of 20 000–100 000 mature individuals (Robertson et al., 2013). But there has been no national survey of this species for nearly 50 years. So, what is its current status nationally? Is the population declining, despite some local increases, or is it stable, but with the main population centres shifting, perhaps tracking changes in food supply? Are a few large breeding colonies being replaced by many smaller, more dispersed ones?

To begin answering some of these questions, Graeme Taylor (Department of Conservation) and members of Birds New Zealand are instituting a survey of breeding colonies over the next couple of years. During the coming breeding season, October 2014–January 2015, our aim is two-fold: (1) to relocate and check the status of colonies known to be active up to 1965; and (2) to look for and record the locations of any new colonies. You can get a list of these colonies and their locations from Peter Frost (birds.wanganui@osnz.org.nz). We don’t need actual counts of the number of breeding pairs at this stage (this will be done next year), but an estimate of size would be useful, as follows: < 10; 10 < 100; 100 < 1000; 1000 < 10,000; and > 10,000 pairs.

Please report any information that you have on the current status of previously known or apparently new colonies to Graeme Taylor (gtaylor@doc.govt.nz), Peter Frost (birds.wanganui@osnz.org.nz) or the appropriate regional representative of Birds New Zealand (see http://osnz.org.nz/contact-us/regional-representatives%20for%20contact%20details). You can also help by getting the word out to your non-birding mates but ones who might be able to provide information.

Once this information has been collated, we will be better able to organize and assign priorities among more detailed (and cost-effective) surveys of the number of breeding pairs, and do so in ways that will cause the least possible disturbance.

Many thanks

Peter Frost and Graeme Taylor

References
Gurr, L. and Kinsky F. 1965. The distribution of breeding colonies and status of the red-billed gull in New Zealand and its outlying islands. Notornis 12: 223-240
Mills, J.A. 2013. Red-billed gull. In Miskelly, C.M. (ed.) New Zealand Birds Online. http://www.nzbirdsonline.org.nz
Perriman, L. and Lalas, C. 2012. Recent increase in population size of red-billed gulls (Larus novaehollandiae scopulinus) at Otago, southern New Zealand. Notornis 59: 138–147
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Peter Frost
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Re: National Survey of Red-billed Gull, 2014-2016

Postby Peter Frost » Wed Dec 17, 2014 10:07 pm

Just a reminder about the national red-billed gull survey being carried out by Birds New Zealand. Most red-billed gulls will now have young(ish) chicks, so the parent birds' behaviour should make the colonies quite conspicuous. We hope that you'll take time to note and report any that you find while out on your festive-season trips (this includes small colonies of only a few pairs). As pointed out above, we are keen to identify the location of all colonies, together with an estimate of the number of breeding pairs (order-of-magnitude estimate only, although anything more precise would be welcome), and a description or photograph of the site.

If you don't have a GPS, you can get the position of a colony by going to the NZ Topo Map website at http://www.topomap.co.nz/. There you can zoom in to the site concerned, using either the scroll wheel on your mouse or the zoom bar at the top right of the page. Once you’ve located the particular site in which you are interested, click on the ‘Coords’ tab on the left of the page. A small green marker will appear that you can then drag to the appropriate position on the map. The latitude/longitude coordinates will appear in the ‘Coords’ box to the left. (You can also use Google Earth; make sure that you activate the Status Bar - under the View tab; you can then read the coordinates at the foot of the image, assuming that you've placed the cursor over the site in question.) The more accurately you can identify the location, the better. You can submit the information either to myself (birds.wanganui@osnz.org.nz) or Graeme Taylor (gtaylor@doc.govt.nz), or the appropriate regional representative of Birds New Zealand (see http://osnz.org.nz/contact-us/regional-representatives%20for%20contact%20details).

We've had a great response from some people. Many, many thanks to them. But I'm certain that we haven't covered all active colonies. You'd be helping greatly if you could look for and report any active colonies. If you happen to search a length of coastline (or an offshore island) and found no red-billed gulls breeding, we'd also like to hear about that.

Many thanks,

Peter
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Peter Frost
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Re: National Survey of Red-billed Gull, 2014-2016

Postby Peter Frost » Sat Oct 03, 2015 9:46 pm

Greetings everyone,

Birds New Zealand, together with the Department of Conservation, is looking to conduct a national census of the red-billed gull breeding population over the next few months. We need your help. Last year we asked people to report any currently active colonies, starting with a check of those colonies reported by Lou Gurr and Fred Kinsky in 1965 (Notornis 12: 223-240) as having been occupied at some stage prior to 1965. Many people responded. Active colonies were reported at 162 sites across mainland New Zealand. A further 19 were recorded in the Chatham Islands. Only about 60 % of the pre-1965 sites were surveyed, just under half of which were still active. A report on this phase of the project is available from the Birds New Zealand website.

We now want counts of the number of active breeding pairs. A list of all 406 currently known present and past breeding sites is available from http://osnz.org.nz/sites/osnz.org.nz/files/1509%20RGB_all%20sites_final.xls. You can view the locations of these sites at http://www.topomap.co.nz/NZTopoMap?v=2&kml=https%3A%2F%2Fdl.dropboxusercontent.com%2Fu%2F102957022%2FRGB_all%2520sites.kml%3Fraw%3D1, where you can zoom into any particular region or site. Clicking on the icon for any site will show our name for the locality. In some cases, the exact locations are uncertain but I’m sure that once you are in the area, locating the colony, if it is active, will be relatively easy. The list of sites that need checking includes those pre-1965 sites that were not checked last year, as well as some additional sites that have been identified subsequently through a review of the Ornithological Society of New Zealand’s Classified Summarised Notes. We have also listed those sites known to have been active in the past but which were reported as being inactive last year. These are clearly identified in the Excel file obtainable from the Birds New Zealand website (see above).

We want you only to count birds on nests and to report the number of active nests (either incubating eggs or brooding young chicks), equivalent to the number of breeding pairs (i.e. one nest = one breeding pair; both members of the pair incubate). How to census the colonies is described in a document that you can download from http://osnz.org.nz/sites/osnz.org.nz/files/Guide%20to%20Counting%20RBG.pdf. We are making arrangements for censusing those colonies on offshore islands and stacks, or in more remote regions, and finding the resources to do this. We may approach some of you individually once we’ve worked out options and logistics.

In addition to counting the number of active nests, where possible, we would like good quality digital photographs of each colony, preferably also with overlapping close-ups of subsections across the colony. This will allow us later to review the counts made in the field and make adjustments, if necessary. Please photograph the colony first, before starting the count, particularly if you are planning to do a ground count. If high quality photographs are not possible, then any others will do. These photographs will form a permanent record of the colony.

If you want to report the number of other individuals present, that should be a separate figure. The variable presence of non-breeders and off-duty partners hanging around the colony means that the total number present fluctuates through time, making it difficult to get an accurate count, whereas the numbers of birds on nests will be constant, at least on the day of the count.

Red-billed gulls should now be pairing-up at colonies. We can expect egg laying any time from early Oct through to December. Ideally, we want to count the colonies at the peak of egg laying. This can be determined by visiting a colony a number of times, something that may not always be practical. A count at any stage of the breeding season is better than none at all, in which case please note what the majority of birds seem to be doing (incubating eggs; brooding young chicks; feeding chicks in or out of the nest).

Please map accurately the location of the colonies either with a GPS or from Google Earth on the maps available at the NZ Topo Map website. If you cannot locate the site on a map and do not have a GPS, then please write down as much detail as possible so we can identify the site later.

Important: if you plan to approach a colony on conservation land, and particularly if you are intending to do a ground count, please contact your local DOC office. Graeme has informed all DOC offices of the census so there shouldn’t be any barriers. Likewise, if you want to census a colony on private land, please get permission first.

Finally, two requests from Dr Jim Mills, who has been studying the red-billed gull population at Kaikoura for over 50 years. First, he will survey the colonies on the Kaikoura peninsula for us and asks that no one else tries to do so, because this could disturb the birds. Second, over many years Jim and his colleagues have been colour-banding red-billed gulls, using a combination of three colour bands on one leg and two plus a metal band on the other. If you see any colour-banded red-billed gulls, please note the colour combinations, reading the bands from top to bottom on each leg, left leg first, then the right leg. You can submit these observations to the National Bird Banding Office (email: bandingoffice@doc.govt.nz).

As before, please send any information (and photographs) to Peter Frost (email: birds.wanganui@osnz.org.nz). We will be happy to answer any queries. All inputs will be acknowledged in the final report and subsequent publications. Thank you all for your support.

Peter Frost, Convenor, Birds New Zealand Projects and Activities Committee, 87 Ikitara Road, Wanganui 4500

Graeme Taylor, Science and Policy Group, Department of Conservation, PO Box 10420, Wellington 6143, New Zealand
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Peter Frost
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Re: National Survey of Red-billed Gull, 2014-2016

Postby Peter Frost » Wed Nov 23, 2016 11:50 am

For those who are interested, a final report on the national red-billed gull survey, to which many members of the public contributed, is now available at http://www.osnz.org.nz/node/836. Many thanks to all who contributed to this survey. This could not have been done without you.

Abstract
The red-billed gull, Larus novaehollandiae scopulinus, is classed as Nationally Vulnerable in New Zealand because of an apparent decline in numbers nationally, especially at some of the largest colonies, and despite some reported regional increases, such as in Otago. A synthesis of known breeding colonies from the late-1800s to the mid-1960s, published in 1965, estimated a national breeding population then of around 40,000 pairs. To update this figure, Birds New Zealand, in conjunction with the Department of Conservation, carried out a national survey during 2014-2016 to establish the current size of the red-billed gull breeding population. Observers were asked to find and report all breeding colonies of the species, starting with a check of previously reported breeding sites. Standardised means of conducting these surveys were developed, publicised, and largely applied. This report summarises the results of this survey and its implications. An estimated 27,831 pairs of red-billed gulls nested in New Zealand in 2014-16 (14,713 pairs at 122 South Island sites; 12,676 pairs at 124 North Island sites; and 442 pairs at 14 sites on the Chatham Islands). Other than colonies on the Three Kings Is (1763 pairs) and Takapourewa/Stephens I. (1250 pairs) there are no large concentrations on offshore islands. The largest mainland concentrations are at Kaikoura (3210), Taiaroa Head (2145), Rotorua (2277) and Marsden Point (1190), some of these close to human habitation. Among the many factors potentially adversely influencing the red-billed gull population, predation and disturbance at breeding colonies, although prevalent, may be less important than changes in food availability offshore during the breeding season. A plan for long-term monitoring of the red-billed gull population is needed beyond the 50-year study ongoing at Kaikoura and the more recent surveys at some colonies in Otago. The red-billed gull is a long-lived, slow-reproducing species in which individual adults do not necessarily breed every year, so any long-term population change is more likely to be revealed by surveys carried out over many years, than by unsystematic counts done at long and irregular intervals. Nationwide surveys, such as this study, are too costly and complex to be done sufficiently regularly to provide accurate and timely information on major population changes. Instead, Birds New Zealand, in conjunction with others, needs to identify several representative colonies around the country, including some nearshore and offshore sites, that are reasonably accessible and for which teams of volunteers are willing and able to survey several times a season over many years using comparable and consistent methods.

Peter Frost (on behalf of Birds New Zealand), 87 Ikitara Road, Wanganui 4500
Graeme Taylor, Science and Policy Group, Department of Conservation, PO Box 10420, Wellington 6143, New Zealand


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