On any given night, some 3,000 migrants sleep on rows of cots inside huge, heated tents set up in an island park with sweeping views of the Manhattan skyline. But as the city struggles to house the influx of immigrants, there simply isn’t enough space in the sprawling complex on Randall’s Island that is now New York City’s largest shelter for asylum seekers. Outside the camp’s gates, a handful of people have pitched their own tents in the cold dead of winter. Many are people who have used up their allowed time in the city’s official shelter system and haven’t been able to get another placement or secure their own place.