Tracking Grey-headed Gull movements around O.R. Tambo International Airport, Johannesburg.

A collaborative project between BirdLife South Africa, Airports Company South Africa (ACSA) and Albert Froneman Consulting.

ACSA Collaboration

Problem Statement

Bird strikes with aircraft cost the international aviation industry millions of dollars per annum as a result of direct damage to aircraft and indirectly due to delays caused by aircraft down time.


O.R. Tambo International Airport (ORTIA) has a world class wildlife hazard mitigation program in place with six permanent staff using a range of methods to address the risks posed by birds on the airfield. The programme is highly effective in addressing bird presence on the airfield. Hazardous bird species often occur in large numbers in areas immediately adjacent to the aerodrome and either fly over the airfield passing through aircraft approach and departure paths or they come to the airfield to feed. Grey-headed Gulls (Chroicocephalus cirrocephalus) are a typical example of a species that occur in large numbers on the pans and shallow wetland areas or open fields around the ORTIA, Johannesburg, South Africa. The wildlife department at the airport maintains a detailed database of bird strikes as well as bird presence and abundance on the airfield. Data from the past 17 years indicate that Grey-headed Gulls rank as a high-risk species at the airport. Given that the gulls often congregate in large colonies near the periphery of the airport and from there venture onto the airfield, it is particularly difficult to mitigate the risks they pose as potential bird strike victims.

In order to develop an effective mitigation strategy to reduce the risk of collisions between the high density Grey-headed Gulls and aircraft at ORTIA, BirdLife South Africa and its collaborators are working together to fill the current knowledge-gaps about the daily and seasonal movements of the Grey-headed Gulls which live close to the airport. The gulls are typically present in larger numbers during the autumn and winter season. It is suspected that the birds forage in a wide area around the airport at landfill sites, shopping malls and various other sites such as compost facilities. Large scale breeding seems to also not take place every year near the airport but the aviation safety risk is significantly elevated when gulls breed in their thousands next to the airport. Gull presence and abundance is much lower during the warmer summer months.

Grey-headed Gull (Photo: Mark Anderson)
Grey-headed Gull (Photo: Mark Anderson)

Aims of the project

Little is known and understood of the movement patterns of the gulls. The purpose of this project will be to establish in more detail the exact movement patterns of gulls over the eastern part of the Gauteng Province with the ultimate aim of using such information to better mitigate the risk these birds pose to aviation safety at ORTIA. Questions we hope to answer with the data collected through the monitoring will include:

  • Daily movement patterns of the birds around the airfield
  • Areas used / visited by the gulls other than the pans and open fields adjacent to the airport
  • Identify potential alternate breeding sites used by the gulls in the eastern parts of the Gauteng Province
  • Dispersal / movement patterns of the gulls during the summer season when their numbers and presence at the airport appear to be much lower

With such information, a better management / conservation strategy could be developed for the Grey-headed Gulls and areas could potentially be identified where breeding could be encouraged at localities where their presence and movement patterns would not pose a threat to aircraft landing and departing from the airport runways.

Methods and logistics


This project has been approved by the Gauteng Department of Agriculture and Rural Development (Permit Number: CPF6-000203) and undergone stringent ethical clearance by the BirdLife South Africa Ethics Committee (Application Number: 2017_01_B).

Tracking devices

This project will use Milsar S9 Radio/GSM solar trackers. These devices are manufactured in Poland and use a solar charging system and the GSM network to log the position and speed of the birds at specified intervals.

Harness testing

Satellite tracking devices have not been attached to Grey-headed Gulls in South Africa before and it was thus decided that prior to the deployment of the selected birds into the field, two “test birds” should be caught and housed in captivity for at least a week. This would allow for the team to monitor the impacts of the tephlon harness and a “dummy” tracking device on their health and well-being. Johannesburg Wildlife Veterinary Hospital were kind enough to provide the two birds with a place to stay during the test period and monitored them twice daily. After extensive testing of the effects of different harness designs on the birds, a suitable fit was found and preparation for the deployment of the three tracking devices was made.

Photo: Melissa Whitecross
Photo: Melissa Whitecross

Trapping the birds

Many ideas were discussed regarding the most effective method for trapping Grey-headed Gulls near ORTIA. After some trial and error, mist nests (fine meshed nets placed between two poles) strategically placed around a lure (a dummy owl) worked out to be the easiest and most efficient way to attract and capture the Grey-headed Gulls. All birds were handled quietly and swiftly to ensure minimal stress. Once the harness and tracking device were attached, the birds were immediately released.

Photos: Albert Froneman
Photos: Albert Froneman

Data collection

The trackers connect to the online server through the GSM network once a day and data points are downloaded for analysis at the end of each month. The preliminary movements of the birds can be seen below.

Our Grey-headed Gulls and their movements


Sex: Male

Weight at capture: 318 g

Name origin: Antonov State Company was a Soviet, and later a Ukrainian aircraft manufacturing and services company. Antonov have built a total of approximately 22,000 aircraft, and thousands of its planes are currently operating in the former Soviet Union and in developing countries. The headquarters are located in Kiev, Ukraine.

After his release, Antanov spent some time in the Midrand region of Gauteng before making a two day journey to the coastline of Maputo, Mozambique where he has remained thus far.


Sex: Male

Weight at capture: 298.2g

Name origin: The Boeing Company is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, and satellites worldwide. It is one of the largest aircraft manufacturers in the world. Its headquarters are based in Chicago, Illinois, USA.

Boeing is the only bird of the three that has remained in the central interior of South Africa. He has slowly made his way to Vanderbijl Park he has remained thus far.


Sex: Female

Weight at capture: 304.7 g

Name origin: Embraer S.A. is a Brazilian aerospace conglomerate that produces commercial, military, executive and agricultural aircraft, as well as providing aeronautical services. Its headquarters are in São José dos Campos, São Paulo State, Brazil.

Embraer is our only female bird at the moment. She spent just over a week in the eastern Gauteng area after release before jetting off to the iSimangaliso Wetlands in KwaZulu-Natal on 2 September 2017. She started her long-haul flight at 18:56 pm and arrived at her destination 11.5 hours later at 06:24 am, with an average flying speed of 10.11 meters/second. She has remained in the Greater St Lucia Wetland area since her arrival.

This is the first concrete evidence of the movement of a winter-based inland Grey-headed Gull to the coast for the summer and could indicate the potential for these birds to be considered coastal migrants. Embraer was the first of our birds to embark on an overnight, long-haul flight to the coast. She has settled into the northern shores of Lake St Lucia and has remained there so far.

Meet the Team

  • Dr Hanneline Smit-Robinson (BirdLife South Africa) is a project coordinator for this research and assisted with the ringing of the tracked birds.
  • Albert Froneman (Albert Froneman Consulting) is a project coordinator and assists with data analysis. He is also the project photographer.
  • Melissa Hofmann (ACSA Bird and Wildlife) is a project coordinator and assists with monitoring the Grey-headed Gulls present at ORTIA.
  • Dr Melissa Whitecross (BirdLife South Africa) is responsible for managing the tracking devices, downloading the data and analysing it.
  • Craig Nattrass is a qualified bird ringer and has assisted with the trapping of the birds and harness fitting of the tracking devices to the birds.
From left to right: Hanneline Smit-Robinson, Craig Nattrass, Melissa Hofmann, Albert Froneman and Melissa Whitecross


  • Thanks to Nicci Wright and Karin Lourens of the Johannesburg Wildlife Veterinary Hospital for housing the two Grey-headed Gulls during the tracker testing phase.
  • Thanks to Malcolm Wilson for his assistance in refining the bird trapping method and capture of the “test birds”.
  • Thanks to ACSA for providing the funds and logistical support to carry out this exciting new research.