The migrants — mostly men — have arrived in Tijuana carrying little, usually no more than a knapsack or a plastic bag. Some also carried toddlers and infants. One woman gave birth this month after crossing the border from Guatemala into Mexico. She was on a bus with her infant the next day for the three-day trip to Tijuana.

The route generally led from the Brazilian interior to Peru, through Ecuador and on to Colombia. Many then took a boat before they started walking again, sometimes for days, through the Darién Gap of Panama, always with a relay team of hired guides, each of whom charged from $10-$20 a head.

Costa Rica became a key staging ground for what many said was the most difficult stretch of the trip: crossing Nicaragua. Getting through that country required a smuggler. Guides charged from several hundred dollars to $1,500 per person and the trip took several days, some of it on foot.

But payment offered no guarantees of safe passage. Haitians here told how their smugglers abandoned their groups midway through the crossing, leaving them vulnerable to bandits or, worse, the Nicaraguan security forces, who returned the migrants to the Costa Rican border. Some migrants got stuck for weeks or even months in Costa Rica waiting for family or friends to wire them money to complete the journey.

At the Mexican border, most Haitians have masqueraded as citizens of the Democratic Republic of Congo. The collective wisdom is that the Mexican authorities treat Africans better than Haitians and are more inclined to give them 20-day transit passes. Real Africans find this masquerade laughable.

“They don’t even know there are two Congos,” scoffed Evans Demorais, 31, a Nigerian migrant here. “They are saying: ‘Please, are you from Africa? What is the capital of Congo? Who is the president?’”