A Wild Bustard Chase in Portugal (and Spain) | Jethro Gauld
Updated: Aug 11, 2020
In April 2019 I joined my Portugal based PhD supervisor Dr João Paulo Silva along with one of his other PhD students Filipa Soares for a week of fieldwork. The aim: Catch and tag as many little bustard Tetrax tetrax males as possible. The reason? This species is currently designated as ‘Near Threatened’ on the IUCN red list but is thought to be in ‘Rapid Decline’ across much of its range aside from France where populations are thought to be stable. Many researchers are now advocating for the species to be listed as ‘Vulnerable’ or even ‘Endangered’. High resolution GPS telemetry can help us better understand the migration behaviour, habitat needs and identify key threats to this species which in turn can inform conservation action to halt the decline. The GPS loggers also carry a number of other sensors such as temperature, accelerometer and barometer so we can remotely relate the behaviour and activity of the bird to environmental factors such as the weather. This field work was also a great opportunity for me to gain more experience in deploying the loggers on smaller birds ahead of fieldwork to deploy loggers on white storks Ciconia ciconia later on in my PhD.
So how do you catch a little Bustard?
JP and Filipa fitting a GPS tracking device to a little bustard male near Castro Verde, Portugal.
In spring the males set up something called a lekking territory – a place in which they display certain behaviours e.g. presenting their plumage (see this video for an example) in the hope of attracting any passing females. Unlike the lekking species we are familiar with in the UK such as black grouse tetrao tetrix; the little bustard males display in an exploded lek which may extend over many hundreds of metres creating overlapping display territories. This can result in fierce fighting between males in adjacent territories when a bird dares to enter his neighbour’s lek. This means that when a female does pass through the area, it can set off a cascade of squabbles between neighbouring males as they try to follow her into territory controlled by other males. JP Silva has devised a system to take advantage of this behaviour. After careful observation we choose the boldest male and place a taxidermy female in a visible location within that male’s territory. Around this ‘female’ we place as many snares as possible to catch the incoming male. If successful it’s then a race for us to get to the bird as quickly as possible, cover it in a blanket to calm it down and remove it from the snare. We then place a hood on the bird to keep it calm while we fit the tag. These birds are quite sensitive to stress so JP keeps other measurements to a minimum, generally just weighing the bird and then fitting the tag, ensuring that it can be released within a few minutes of capture.
The taxidermy female used to lure the male birds.
This trapping technique works best where there is a high density of males and competition for mates is high, in areas where there are more females they seem to be able to tell the difference between the real deal and the fake bird. In these cases sometimes JP deploys a taxidermy male bustard along with a recording of the male’s display call to get the male fired up - thinking that another male is courting a female in his territory!
Unfortunately for these birds along with other species of the Steppe, Portugal and Spain are experiencing rapid changes in land use. This is driven largely by subsidies driving greater intensification. These incentives are causing a rapid loss of traditional land management practices. Mixed agriculture systems based on crop rotation where adjacent fields are left fallow in particular years between harvest years and remnants of the original steppe forest (Olive and Cork Oak Trees) are maintained within systems used for grazing and growing cereals provide the perfect habitat for a plethora of animal and plant species. Including characteristic birds of the Steppe including the little bustard, the great bustard Otis tarda and Black Vulture Aegypius monachus to name a few. These traditional systems which have been in place for centuries are now being rapidly replaced with intensive monocultures of Barley, Wheat, Olive Groves and Vineyards with high inputs of agro chemicals and no space for wildlife. This means that the vital flower rich habitat these birds rely on is becoming more fragmented from one year to the next. During our week of fieldwork we visited a large number of sites in Spain where lekking males had been present in 2016. We did this to identify suitable sites for trapping little bustards; unfortunately we found that approximately half the sites were now dominated by intensive agriculture and the birds just weren’t there anymore. Understanding the movement of these bird will help us identify priority areas for protection.
A tale of two agricultures: on one side of the track a small wildlife rich fallow as part of a system managed in the traditional way and on the other side an intensive cereal monoculture as far as the eye could see.
The story of the little bustard is not unique, there are similar examples in most biomes. New protected areas are a vital conservation tool but they cannot solve this problem alone; this is yet another case where conservation is coming up against the pressures placed on our environment by a society built on an ever growing demand for resources. In this case resulting in the replacement of sustainable, wildlife friendly agricultural practices with unsustainable monocultures on a vast scale.