Will they tern up?

Courtney Hamblin is doing a Master of Science at Lincoln University. Here she tells us about her current research.

We have all experienced that moment of anxiety and anticipation: you have organised an event or party and you nervously await the arrival of your first guests. You know people have responded to your invites, but you check it for the thousandth time just to be sure. I have become very familiar with this feeling over the last few months, sitting in braided rivers throughout Canterbury. The only difference being that my guests are of the feathered kind. This spring/summer I have been trekking around nine of Canterbury’s braided rivers in the hope that the endangered, black-fronted tern may be attracted to my set up of tern calls and decoys.

Decoys (spread out in the foreground) and audio playback (housed in the cage seen in the middle, right side of the picture) set up in the Potts River

The idea was that birds that breed in colonies, such as the black-fronted tern, are attracted to locations where there are others of their own kind (also known as conspecifics). The presence of conspecifics is thought to be an indication that the location is a quality breeding spot. Being drawn to other individuals of your species may also increase your chance of finding a mate. My project aims to test this idea using tern calls and decoys to imitate a real tern colony, to see if the real terns will interact and possibly breed at chosen areas.

Black-fronted terns are an endemic New Zealand seabird, which breed almost exclusively in braided rivers. Growing up in Canterbury, braided rivers, such as the Rangitata or Waimakariri, appear to be common place, when in fact they are a rarity internationally. The braided rivers in New Zealand represent a significant proportion unmodified braided river habitat on a global scale.

Black-fronted tern (Adult)

Life on a braided river is not easy. Braided rivers are dynamic and hostile environments, experiencing everything from raging floods and snow, to extreme winds and oppressive heat. All lifeforms inhabiting these environments have been forced to adapt in order to survive. Black-fronted terns are very well adapted to the braided environment; for example being able re-nesting up to four times in a single breeding season to cope with flooding events. No matter how well adapted they are to cope with the harsh braided river environment, the terns have no defense against the more recent arrivals. Introduced mammalian predators and plant invaders now threaten their habitat and survival.

The protection and conservation of black-fronted terns is completely reliant on our ability to manage them in their mainland braided river environment. Sadly no suitable braided river habitat exists on the predator free offshore islands, eliminating this as an option for black-fronted tern conservation. Due to their unpredictable nature, management in the braided river environment is very difficult. The terns further complicate the matter as they are notoriously fickle with respect to their breeding locations. Each year when the terns return to breed in the braided rivers, or even re-nest within a breeding season, they will often move substantial distances from their last breeding location. The unreliability of tern breeding locations makes them very difficult to manage effectively, as we can never be sure of where they will decide to go. This is where my research comes in; if using decoys and audio playback can attract the terns into an area to breed we may be able to manage them more effectively. Fingers crossed we can get the terns to come to the party!

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