Forum News 37 article: Ocean climate and Rockhopper penguin foraging strategies

Purpose

This project will help to understand why rockhopper penguins have declined dramatically in the Falkland Islands, and to propose and evaluate conservation measures.

Context

The population of rockhopper penguins (Eudyptes chrysocome chrysocome) in the Falkland Islands has declined by over 80 % between the 1930s and 1995 (Putz et al., 2003). Since 1995, numbers seem to be stable (Clausen and Huin, 2003; Putz et al., 2003). Numbers of breeding pairs at proposed research sites on New Island are stable (Catry; Poisbleau; Strange, 2007 pers.com).

Population declines have also been observed in other subspecies of rockhopper penguins (Guinard et al., 1998; Thompson and Sagar, 2002) and possible reasons are believed to be changes in sea surface temperatures causing changes in distribution and abundance of prey (Boersma, 1987; Cunningham and Moors, 1994; Guinard et al., 1998; Putz et al., 2001) as well as a general shift towards lower primary production (Thompson and Sagar, 2002; Hilton et al., 2006). Interaction with fisheries has also been discussed in the case of rockhopper penguins in the Falkland Islands (Thompson, 1989; Putz et al., 2001).

Some information exists about the distribution of rockhopper penguins at sea during winter migration (Putz et al., 2002) as well as during the breeding period (Boersma et al., 2002). Rockhopper penguins disperse widely during winter migration (Putz et al., 2002), but they have to return regularly to the colony during breeding, therefore being limited in their foraging range.

Differences in diving behaviour have been found for rockhopper penguins in the Falkland Islands and other breeding sites. Those differences are believed to be due to food availability as well as habitat structures (shelf vs. oceanic waters) and might explain differences in population trends (Schiavini and Raya Rey, 2004; Putz et al., 2006).

As other Eudyptes species, rockhoppers present a synchronised breeding pattern with well 10 defined times of foraging and nest duties for males and females (Strange 1982). Males leave about two to three weeks after the eggs are laid, staying at sea for seven to ten days. After the return of the male, females leave and return just in time of chicks' hatching. During the guard stage, only the female forages and feeds the chicks, whereas once crèches have been formed, both partners forage for food. During the guard and creche phase birds usually return daily, therefore assumingly foraging closer to the colony (Strange, 1982). Boersma et al. (2002) found two distinct types of foraging trips. Short trips lasted less than three days and birds foraged less than 10 km away from the island whereas on long trips, birds stayed away from the colony for over three days covering large distances. The maximum distance reached was between 168 and 469 km (Boersma et al., 2002). Unfortunately, breeding stages are not indicated in detail; differences in foraging trip length and distances travelled might be due to different breeding stages. Mattern (2006) studied the foraging behaviour in the conspecific Snares penguin (Eudyptes robustus) and observed birds using distinct foraging areas and oceanographic features during incubation and chick rearing. Females during chick rearing were limited to areas closer to the colony, feeding in warmer coastal waters, whereas incubation trips of males reached the Subtropical Front on longer foraging trips (Mattern, 2006).

Oceanographic conditions play a major role in the distribution of seabirds at sea (Haney 1986; Hayes and Baker, 1989; Schneider, 1990, Weimerskirch, 2001), due to the patchy distribution of prey organisms related to oceanographic features such as upwelling, eddies and fronts (Schneider and Piatt, 1986; Hunt et al., 1990; Weimerskirch et al., 1994; Vlietstra, 2005; Weimerskirch, 2007).

A detailed knowledge of foraging areas and oceanographic conditions around breeding colonies in the Falkland Islands is therefore essential in order to understand population trends of rockhopper penguins. Raya Rey et al. (2007a) showed that heterogenous oceanographic conditions off southern Argentina enhanced biological activity thus causing better food availability for rockhopper penguins. A relationship between food availability and reproductive output has been found, due to better provisiong rates (Raya Rey, 2007b). If males and females would use different foraging areas, males could presumably buffer changes in provisiong rates by females as has been found by Trembley and Cherel (2005).

Spatial and temporal variation has been found in the diet of rockhopper penguins in the Falkland Islands (Strange, 1982; Thompson, 1989; Clausen and Putz, 2002), which could be related to different foraging areas used by adults during incubation and chick rearing.

In thin-billed prions from New Island, chick mass and feeding frequencies are correlated with sea surface temperatures but birds seem able to buffer for poor food conditions since breeding success was found to be insensitive to oceanographic conditions (Quillfeldt et al., 2007). Considerable remotely sensed and real time ocean data exists for waters around the Falkland Islands. However, the oceanographic data has not been matched to the penguin data. In this study, penguins will also be used directly (through the use of data loggers) for monitoring environmental conditions (see Wilson et al., 1993; Weimerskirch et al., 1995;Charrassin et al., 2004; Sokolov et al., 2006).

The combined use of data loggers, transponder technology, and diet sampling at the New Island rockhopper colony will provide crucial information about the foraging behaviour of rockhopper penguins. Monitoring programmes that, so far, mainly focus on land based indicators, will be extended to the essential at-sea phases and the effects of the of ongoing climate change on seabird population. This information will play a key role in the development of protection measures and could be used to adopt a standardised approach for other populations and species of Eudyptes in UKOTs.

For References:
Email: cquick@ukotcf.org

Outputs

1. Data published in scientific and popular scientific literature

2. A database of oceanographic data.

3. A GIS model of these data.

4. We aim to make all outputs as widely available as possible. A new web-based tool is being developed at the Max Planck Institute (MoveBank), and the data will be deposited and made available here.

5. An information pack will be produced and presented at the local school, along with community talks to raise awareness.

Main Activities

• Transponder tracking & weighing bridge

  Since 2006/07, over 500 rockhopper penguins at New Island have been equipped with PIT tags, allowing the monitoring of large numbers of individual birds without disturbance to the colony. A weighing bridge, which includes an infrared beam to detect direction, a PIT tag reader and weighing platform, has been installed at one of the access points to the colony. These devices enable us to monitor departures and arrivals of birds from the colony, including their weights. These data will be used to calculate food loads brought back to the chicks by foraging adults. Foraging trip lengths can be calculated during the entire breeding period and even in unmarked birds, sexes can be determined by the weight measured (females being lighter than males) which leads to a better understanding of breeding and foraging patterns over the entire breeding period (see below).

  The implementation of this important part of the project has been financed through a grant of the German Research Foundation DFG, but follow-up funding for the project is now needed.

• GPS TDlog data loggers

  GPS data loggers will be deployed on breeding rockhopper penguins at New Island during different breeding stages. Devices record the birds' positions at sea in defined time intervals and allow a very detailed analysis of foraging tracks. Differences in trip durations and especially in the use of foraging areas can thus be detected between incubation, guard and creche stages and between male and female birds.

  The devices include high-resolution depth and temperature sensors, allowing a fine-scale analysis of diving behaviour as well as water temperature analysis. Oceanographic conditions will be identified along horizontal as well as vertical tracks swam by individual birds. Rockhopper penguins from Staten Island, Argentina, are believed to forage at fronts (Raya Rey 2007a) and such features could be detected using data logger based temperature data. Data on water temperature can subsequently be incorporated in oceanographic models (see Sokolov et al. 2006, Ludynia 2007), being of great use for monitoring environmental changes. Diving behaviour in penguins can be directly related to prey abundance; diving effort is a good proxy for food availability and might partly explain provisioning rates and breeding success. Data loggers have been purchased through funds made available by the Max Planck Institute for Ornithology and can be used during the entire duration of the project.

• 9 Stable isotope analysis

  Analysis of stable isotope ratios in animal tissues has emerged as a powerful tool for determining the trophic level and composition of prey and foraging location. Using this method, it is possible to reconstruct diet types from isotope samples taken non-invasively (e.g. moulted feathers, egg membranes), if the diets consist of isotopically distinct components. Tropho-dynamic research using stable isotopes generally focuses on carbon and nitrogen, since the isotopic ratio of these elements varies in relation to the diet, trophic level, and foraging location (e.g. Quillfeldt et al., 2005; Gladbach et al., 2007; Weiss, 2007; Quillfeldt et al., in press a,b).

  We will collect samples for stable isotope analysis and apply for a co-operative project to have them analysed in the framework of a grant-in-kind at the Scottish Environmental Research Centre, UK. Many of the samples used in stable isotope analysis can be collected non-invasively around the colonies (e.g. moulted feathers, egg membranes) and can be used to explain site- and year-specific differences in diet and foraging.

• GIS and remote sensing data

  Data obtained from the GPS TDlog data loggers will be incorporated into GIS and will be further analysed in relation to bathymetry and other environmental factors. Remote sensing data, such as satellite images of sea surface temperature and chlorophyl a will be combined with foraging tracks and diving data from logger equipped birds in order to explain the importance of specific oceanographic features for foraging penguins. The resulting GIS models may also be used to explain the distribution of other seabird species breeding at New Island.

Stakeholders

The Rockhopper penguin is listed as a Key species under Species and Habitat Action Plan Biodiversity Strategy for the Falkland Islands. Monitoring and evaluation of this project will be through the FIG Environmental Officer. Here, we will also coordinate the data the government needs most for the protection of the marine biodiversity. Dr Petra Quillfeldt participated on behalf of the NICT in the International Workshop on rockhopper penguins, organized by the Environmental Officer (FIG Environmental Department) and Falklands Conservation / BirdLife. This workshop brought together a number of Stakeholders from other Territories (Tristan da Cunha) and countries such as Chile and Argentina. Dr Petra Quillfeldt co-authored the forthcoming report Rockhopper Penguins: A Plan for Research and Conservation Action to Investigate and Address Population Changes. Rockhopper penguin does not compete directly with commercial fisheries, instead, data on the distribution and success of Rockhopper penguins can provide valuable information to fisheries scientists and managers at the FIG Fisheries department.

NICT supplies data on penguin population numbers to FC as part of their monitoring programme, and will exchange data and samples with several complementary studies on rockhopper penguins in other countries as agreed at the above mentioned workshop.

Critical Assumptions

Risk 1: External risks: breeding failure due to adverse conditions
Probability: Low
Impact: Medium (some data not available in such a year)
Management: Scientific analysis of the climatic causes

Risk 2: Internal risks: personnel leaving before completion
Probability Low
Impact: Medium (time investment in training/replacement)
Management: Train students from beginning, keep all data on database.

Wider Significance

We will contribute to research on a species of conservation concern.

We will contribute to a monitoring programme for rockhopper penguins that could be extended across other populations and species of Eudyptes in UKOTs.

Data collected in the proposed project can also help to understand the impacts of climate change on marine top predators and its prey, including economically important marine organisms such as commercially exploited fish and squid species. Thus, the oceanographic data will be made available to the Falkland Islands Government and other non-governmental research and conservation bodies.

The project will contribute to local livelihoods through education, in local media and community talks. It will indirectly benefit the community (local and global) by enhancing our understanding of both regional ocean climate and the use of oceanic resources by a seabird, and by contributing to the protection of this threatened species. The knowledge gained will also contribute to understanding ecosystem processes that are important for the local economy.

Other Information

Funded by FCO/DFID Overseas Territories Environment Programme, 2009, project no FAL603

Multilateral Environmental Agreements

Convention on Biological Diversity

e.g. Article 12 b Promote and encourage research that contributes to the conservation and sustainable use of biological diversity.

Convention on Migratory Species