Crown Prince of UAE Sheikh Mohammed bin Zayed bin Sultan Al Nahyan and Bahrain ruler Hamad bin Isa bin Salman Al Khalifa have reached Pakistan on a private hunting trip, reported 24NewsHD TV channel Friday.

Both the royals would go on a hunting expedition in the Cholistan area of Punjab.

These secretive private hunting expeditions date back over four decades and have continued even after Pakistan’s Supreme Court imposed a blanket ban on the killing of the houbara bustard in 2015. The order was later reversed.

The houbara bustard is a large terrestrial bird found in parts of Asia, the Middle East and Africa. The North African houbara (Chlamydotis undulata) and the Asian houbara (Chlamydotis macqueenii) are separate species. The Asian houbara is related to the critically endangered great Indian bustard native to India.

After breeding in Central Asia during the spring, Asian houbara bustards migrate south to spend the winter in Pakistan, the Arabian peninsula and nearby Southwest Asia. Some Asian houbara bustards live and breed in the southern part of their ranges including parts of Iran, Pakistan and Turkmenistan.

According to the International Fund for Houbara Conservation (IFHC), roughly 42,000 Asian houbara bustards and over 22,000 of the North African houbara bustards remain today. The main reasons for the decline in the species’ population are poaching, unregulated hunting and the degradation of its natural habitat.

Vast swathes of land in Pakistan are allocated in blocks to wealthy dignitaries from the UAE, Saudi Arabia and other Gulf countries, who arrive in the country to hunt the birds every year using hunting gear and falcons. They kill the bird for sport and also because its meat is supposed to have aphrodisiac qualities.

For over four decades, the Pakistan Foreign Ministry has been extending yearly invitations to wealthy and powerful Arabs for hunting houbara bustards in the deserts of Balochistan and Punjab, to strengthen the country’s relations with Gulf nations. Arab hunters first started coming to Pakistan to hunt in the 1960s after the houbara bustard population in the Arabian peninsula began to dwindle.