Their melodious song injects a joyful energy into this otherwise drab, dusty refugee camp located on a desert plain in Jordan's north near the border with Syria. Abu Bilal wishes his unusual pet shop in Zaatari Camp will cheer other Syrian refugees clinging to the last thread of hope to return home.
As Syria's civil war has entered its fifth year, refugees sheltering in Jordan's largest camp expressed despair for the future, saying they never expected the conflict to have lasted so long or to have brought so much destruction to their beloved homeland.
"The situation is terrible in every way imaginable," said Mohamed, 25, who sells used shoes in the camp. He would give only his first name fearing retribution for relatives back home.
"Whether it's our Arab neighbours or foreign countries, they have all abandoned us to the regime's brutality and that of the extremists who are trying to gain more control and territory," he said, referring to Islamic State and other militants operating in Syria.
Mohamed said he has been in Zaatari for two years since fleeing Daraa, a southern Syrian town about 15 miles away and the cradle of Syria's ill-fated revolution that began in March 2011.
"Our country was once stable and secure," Mohamed said, his voice full of desperation. "Now we could only hope to return to Syria if the Americans, Arab countries and others intervened on our behalf."
In mid-March, the Assembly of the Catholic Ordinaries of the Holy Land expressed concern that "Syrian and Iraqi refugees living in difficult conditions in Jordan are losing hope of returning to their countries."
The assembly urged the international community to intervene in order to help ease the refugees' "desperate situation."
The United Nations refugee agency said the ongoing conflict in Syria has produced the greatest number of refugees in modern history. More than 220,000 Syrians have lost their lives and 11 million others have been displaced in more than four years of armed conflict, according to the U.N. High Commissioner for Refugees.
The crisis has sparked a humanitarian catastrophe as international assistance has declined despite growing numbers of refugees in the region. Jordan and other countries that have taken in people are doing what they can to help, but they struggle with scarce resources.
In 2014, just 37 percent of the $2.3 billion requested for humanitarian needs in Jordan was received for donor nations, according to Jordanian Planning Minister Imad Fakhoury. He added that despite being nearly a quarter of the way through 2015 in late March, the country's refugee assistance program remains 5.5 percent funded.
Jordan said it hosts about 1 million displaced Syrians, while the U.N. reports there are 600,000 registered refugees in the country. Most live in squalid conditions with up to 3 families sharing a single apartment while others house in three refugee camps.
There seems to be no end in sight yet to the fighting in Syria, which began with anti-government protests before escalating into a full-scale civil war pitting the mainly Sunni majority against President Bashar Assad.
The conflict has fueled violent Islamic extremism, with Islamic State militants taking control of abandoned cities and imposing their own brand of Islam on those they seek to subjugate. Islamic State forces and the al-Qaida-backed al-Nusra Front have spent more time targeting the so-called moderate Free Syrian Army fighters than the Syrian regime.
Syrian refugees such as Abu Omar say that if Assad is removed from power, the Islamic State and other extremist groups would diminish.
"Most of the Islamic State militants are foreigners, not Syrians. Assad allowed such fighters to enter Syria," said Abu Omar, who uses his Arab nickname, rather than his real name fearing retribution against relatives in Syria.
Abu Omar and other refugees said the presence Iranian and Lebanese Hezbollah fighters in the Syrian conflict gives Sunni Muslim extremists further pretext to use Syria as a battleground to fight the Shiite Muslim allies of Assad.
"If you remove Assad, then you will remove Islamic State," shopkeeper Abu Ahmed said.
But one of the camp's older residents dismissed such talk. "If you get rid of Assad, he will be replaced by a 100 more Assads in the future," said a 70-old woman named Um Kiffah.
"What we all think about is whether we will be able to return to our country," said Abu Bilal, the canary seller.
"We don't know what will happen, but we are here until the war ends," he said. "God willing, terrorism will leave Syria whether it comes from the Islamic State or the regime."