Interview with seabird researcher Dr. Benjamin Metzger

July 14, 2015 12:27 pm
By Ketija Riteniece

When I had the chance to do fieldwork for the first time with the Malta Seabird Project team, we were going to a nearby islet to ring shearwaters as they are returning to their nests. The sun was setting down, Benjamin was inflating the kayak to access the islet with, and I thought: No way, this cannot be a real job. Project researcher Benjamin Metzger has spent almost four years in Malta working to protect Maltese seabird species: Yelkouan Shearwaters (Garnija), Scopoli’s Shearwaters (Ċiefa) and Mediterranean Storm-petrels (Kangu ta’ Filfla). This work is challenging, yet very fascinating, and I thought it would be unfair to not share the full interview with the researcher that was originally held for our magazine Bird’s Eye View.

What led you to come to Malta and work with seabirds here?
I have been working with seabirds on research vessels in the Baltic and the North Sea. There I got fascinated by Northern Fulmars. I have also been volunteering on La Palma island in Canaries, where a very small population of Manx Shearwaters is left. They are highly influenced by invasive species like cats and rats. To hear their weird calls at night in the barrancas, these deep canyons, is really amazing. I saw that Life project in Malta is a very good opportunity for me to work with this group of birds – tubenoses, so I applied for a job application.

What are the main differences between working in these places and working in Malta?
There is of course a huge difference regarding culture and climate. Also, here in Malta we have an opportunity to work on all seabirds on this group of islands, which I think is something special. But seabirds worldwide – this is true for the Baltics, true for the Mediterranean, everywhere – they are facing massive declines and have a lot of threats.
Why is that so?
In the Baltics, it is for sure that the main threat is the gillnet fishery, but here in Malta we don’t know yet. We know that to some extent that it is long lining – shearwaters get caught in both traditional and industrial long lining. Worldwide seabirds are facing the most dramatic decline rather as an ecological group of birds, than a taxonomic unit, because seabirds include tubenoses, penguins, gannets, pelicans etc. The main reason is that they are restricted to rather small areas when it comes to nesting.

“If their nesting area is being developed or infested by alien invasive species, they have nowhere else to go.”

Seabirds always come to nest to the same spot; we call it high site fidelity. Even if their distribution range is enormous, covering large stretches of sea, the actual breeding sites are very tiny. Furthermore, island environments are usually very sensitive towards invasions by non- indigenous species.
Is it true that rats are a problem at seabird nests?
In many seabird colonies, rats and other small rodents are a problem. They are attracted by litter and will eat seabird eggs and chicks. The only site in Malta where rat control is carried out is Rdum tal-Madonna, where the largest colony of Yelkouan Shearwaters nests.  We carry out rat control there every year during the breeding season to protect the nesting birds. We have an indication that around 60 % of eggs and chicks used to be eaten by rats and now none are, with no indication of losses to rodents for at least three years. This work has been made possible thanks to financial aid from MEPA and HSBC over the years. However, complete rat eradication there is not possible, because Rdum tal-Madonna is a peninsula. If it was a small, uninhabited islet 2-3 km from land, for instance, eradication would be much easier. But rats can swim back or be brought by ships, therefore a permanent bio-security fence is needed. In case there is a re-colonisation, then it is immediately noticed and they can be eradicated again.
In November the LIFE+ Malta Seabird Project will announce the marine Important Bird Areas (IBAs) that you have found. What does this mean and what will change in these areas?
Marine IBAs are areas which contain a significant proportion of a seabird’s population, either one species or species community, which the birds use for breeding (these IBA’s are on land), rafting or foraging. Or they may be key sites for seabirds on migration, the so-called bottle-necks like Gibraltar or the Bosporus, where they are especially vulnerable because many birds have to cross this narrow gap in a short period of time.  EU member states are required to declare marine protected areas so that these sites become legally protected, in the same way that nature reserves are protected on land. BirdLife International has defined a toolkit how to identify IBA’s, also especially for the marine environment. And most countries agree that the bases of marine protected areas are the IBA’s, important bird areas. Then they are declared as special protected areas within Natura 2000 network of the European Commission. The next step is to create management plans for the areas, setting out steps which will protect seabirds.
What steps would this plan ideally consist of?
For example, if an Important Bird Area in the Baltic sea has a very strong interference between diving sea ducks and gillnet fishery for herring, meaning that a lot of these birds get drowned in the gillnets, then the management plan would ideally conceive these areas completely free of gillnets or any kind of fishery (which in most cases would not happen) or limit the fishery to a certain time of the year, to a certain depth of the water, which is not used by the ducks. Also, the fisheries might have to develop mitigation measures to reduce the bycatch. A management plan could also forbid offshore wind farms within the rafting sites of shearwaters, for instance.
But some problems like light and sound pollution, and plastic waste, cannot be mitigated by declaring IBAs?
Yes, at least so far. Light pollution can be limited. Marine protected areas can also be on land close to seabird colonies, where the management plan can determine that light pollution has to be either reduced or at least not increased. Often it is not even expensive and actually saves money.
Why were exactly these three species chosen for this project?

Malta has no other strictly marine seabird species, which have an unfavourable conservation status. Actually, we can’t say ‘species’ because only two of them have species status. The Mediterranean Storm-petrel is still considered a sub-species of a European Storm-petrel. But all three, let’s say, taxonomic units are either endemic or near endemic to Mediterranean base.

“And we can say for sure, that not all storm petrel colonies are mapped, properly assessed or even found yet. But for the moment more than 50 % of the Mediterranean Storm-petrel nest on Filfla Island – the small island of a size of maybe two football pitches.

This makes this place so important and Malta’s obligation is to safeguard their future. When it comes to the Yelkouan Shearwater, we speak of about 10 % of the global population breeding in the Maltese islands. With Scopoli’s Sherwater it’s currently unclear, because a recent publication  states that there are about 140 000 pairs nesting on Zembra island belonging to Tunisia. If these numbers are correct, it means a three times higher global population size than previously estimated. Some seabird researchers have their doubts.

What makes this project more important – that Malta holds a high percentage of the global population of these species, or that their numbers are declining locally? I mean, should we protect species that are disappearing from our country, whilst being abundant elsewhere?
For instance, the Yellow-legged Gull in some Mediterranean countries is even controlled as a pest species, but in Malta it is rare and legally protected. Nevertheless, we would not search for important bird areas for Yellow-legged Gulls here. Usually, to declare a marine IBA, you consider percentages of the global population that use this area regularly. But you can declare an IBA on a country level as well, for instance, for Maltese seabirds only. The Scopoli’s Shearwater on the IUCN red list is listed as of Least Concern (regardless if the numbers on Zembra in Tunisia are counted or not), meaning that the global population is still huge. On the other hand, a general decline has been noticed and the adult survival rate is not high enough (at least for some regional populations) to maintain the global population at the level it is now.
Speaking of Yellow-legged Gulls, they attack storm petrels. Is it acceptable to restrict one species in order to protect another?

This is a very complex topic, especially here in Malta. One of the actions in our project is to assess the so called interspecies conflict between the Yellow-legged Gull and the Mediterranean Storm-petrel on Filfla. When we go there, for instance, to map the gull’s nests, we find pellets that they regurgitate. Quite often we find remains of storm petrels in these pellets, mostly from adult storm petrels. It is extremely difficult to quantify what amount of them are predated by gulls each year. Many regurgitate pellets fall into the sea. We also don’t know what would be the natural predation rate – how many storm petrels could be eaten without an effect on population size of this colony. There might be a problem, but we can’t properly quantify it, so at the moment I don’t see it justifiable to take management measures towards the gulls. At the moment we try to monitor as accurately as possible the population numbers and reproductive success of both species. There is a similar problem on Benidorm island in Spain, only there storm petrels don’t nest in small crevices like in Malta, but openly in large sea caves, so the Yellow-legged gulls can take not only the adults, but also the eggs and chicks. What helped a lot was introducing nest boxes with an entrance tube, so that the gulls can’t access.

“Gulls are opportunistic feeders, they eat what is common and easy accessible. But on Benidorm it seemed that very few individuals from the gull colony were actually specializing on storm petrels.”

So what they did is they removed just these individuals and had much lower predation rates. The problem there is also light pollution, as the island is close to a quickly developing tourism area. These sea caves were originally in darkness, but now even if the storm petrels come back at night, gulls can see them and forage on them. This would not be the case, at least not that much, if there was no light pollution.

It seems that working on seabirds is more challenging because they are out at sea, where it’s hard to reach for humans, and then only come in to their nests on land when it is dark.

Yes, it’s true. One important tool for our research are the boat based observations. To study the birds at sea, you need to have a really good vessel, able to manoeuvre rough seas, which is usually expensive. The other important tool to find the whereabouts of seabirds in the marine environment is tagging them with tracking devices, but for this you need to go into colonies at night, and sometimes spend the whole night just waiting for some tagged bird to return. They might be out at sea for weeks and you don’t know when a bird will come back.

“We had Scopoli’s Shearwaters, where one partner stayed on the egg for 21 days, and the other was just out at sea.”

Next, most of them nest in the least accessible places. You often need to reach them from ledges, climbing with ropes. The rock where seabirds nest is often quite unstable, because there are so many crevices and holes. And they do not nest just half a meter or a meter deep, but sometimes in small holes where it is impossible to reach them. So you only get access to these birds when they are on their way in or their way out. So you spend night after night after night waiting for the bird to come back. Sitting on a cliff ledge on cold and often windy nights in January and February makes the work challenging.

How do you study seabirds with boat based observations?
What we did for the first two years of the project, is basically sailing on a transect line (for total of 224 days) and counting birds following a standardised procedure. Every five minutes a snapshot and coordinates are taken. Later on you can calculate seabird densities from this data for certain sea areas. However, we do not know if the birds that are counted at sea are Maltese birds or they come from a colony in Sicily or elsewhere. Second, we only covered 25 nautical miles, a circle around Maltese islands, where Malta has exclusive rights to fish and where its government can declare marine protected areas. Nevertheless seabirds fly so much further. We are also interested where exactly our birds go, and that’s where the tracking with GPS devices comes in. We use data loggers which receive information about their location from GPS satellites every 10 or 20 minutes and store it. After retrieving device from the bird, you download the data and know where exactly it spend what amount of time, how quickly it travelled etc.
What are the conclusions from the data that GPS devices have brought?
Very important areas for these birds are really far from Maltese waters, for instance, in front of the South-eastern corner of Sicily there is a hotspot for both Scopoli’s and Yelkouan Sherawaters. Other Yelkouans are flying to Gulf of Gabes in Tunisia – a large, shallow area, probably nutrient rich with a lot of small fish. Many of the Scopoli’s also forage close to the Libyan cost. We were also putting different devices called geolocators that calculate the position by the time of sunrise and sunset and can stay on the bird up to one or two years. From these data we calculated that outside the breeding season, Maltese seabirds fly as far south as Namibia or Angola to forage there in upwelling areas in the East Atlantic.
The project has been going on for three and a half years. What have been your best moments during the project?

One of the best moments was when we caught a Storm-petrel that was ringed 27 years ago on Filfla. Imagine, it’s a bird of a size of a sparrow but has had an amazing life history! When recaptured, it looks exactly the same, at least for us. But it has been travelling presumably to somewhere in the Atlantic and back every year. Another great moment was finding an incubated egg, and later a young chick, in one of the nest boxes we had set up for Yelkouan Shearwaters.

“This was actually one of the first examples anywhere in the world of Yelkouan Shearwaters using a nestbox.”

Also, retrieving the first tag, downloading the data and knowing that this method works.

Have there been any disappointing moments?
The hardest moment is finding birds shot in front of their nests, some people are killing them for fun. Also, if a tagged bird comes back after four weeks and you find that salt water has entered and damaged the tag, so all the data has been lost – things like that are disappointing from the scientific perspective.
Do you think that events and lectures during the project bring awareness to Maltese people about seabirds and their needs?
I think that in Malta the awareness about seabirds is not too high, because you can’t admire them during the day, and for many people seabirds don’t seem that enigmatic either, in comparison with raptors, for instance. Nevertheless, I think we did raise awareness and still do. Certainly with some press work. I think what really raises the profile is nest cameras, so that you can look into their home and into their life and have an impression on what is going on there.
What are the things that amaze you the most about seabirds?
On one hand they are almost human like in some aspects. They show a high site fidelity, returning to the very same spot every year to nest. They grow tremendously old – that is quite interesting. They show faithfulness to their partners as well. But on the other hand, imagine how different their world is from ours. How they orient in the open ocean with hardly any visual clue, how they find their small island and nest entrance in pitch darkness, coming back from thousands of kilometres away, just by the smell. How they can spend days without using energy, just by using these tiny upwinds above each wave to fly, travelling huge distances within a very short time. This makes them quite fascinating to study.