Shirts and signs at the National Puerto Rican Day Parade in Manhattan noted the recent estimate by public-health experts on Hurricane Maria’s death toll on the island.

In the beginning, and the middle, and the end, as always, there was the Puerto Rican flag: countless thousands of them waving as the National Puerto Rican Day Parade marched and danced up Fifth Avenue in Manhattan on Sunday in the steady drizzle, flags worn as ponchos, flags adorning T-shirts and hats and flip-flops.

But there was also a different version of the flag on display this year: black and white instead of red, white and blue, stripped of color to remind spectators — and anyone in Washington who might have been watching — of the parade’s grim backdrop: the destruction and continuing aftermath of Hurricane Maria, and what many view as the federal government’s inadequate response to the disaster.

And there was another new symbol, emblazoned on banners and T-shirts: a number, 4,645, representing a recent estimate by public-health experts on the hurricane’s death toll on the island, far in excess of the official death toll.

Revelers lined Fifth Avenue in Manhattan to watch the parade.

The 61st annual parade, held under gloomy skies, was part party, part protest march, part memorial, part pep rally, sometimes all in one person.

Maria Torres stood behind the barricades on a block of Fifth Avenue lined with high-end boutiques, cheering and waving at the floats. She wore a ball cap that said “Puerto Rico se levanta” — Puerto Rico rising — and carried a sign: “I’m from Luquillo, P.R. I am a Hurricane Maria survivor! Yo no me quito:” I’m not leaving.

Ms. Torres, 55, said she had traveled from her hometown on the island’s northeast coast to deliver a message. “What they say is not true about the death toll,” she said. “I was there. I saw. And even my own sister-in-law died that night. She died because she was in intensive care when everything was shutting down.”

Her message…