While hiring in the U.S. rebounded in March, baby boomers who are still in the work force are not doing so great.

Employment for people age 55 and older dropped 209,000 last month, the biggest such decline since February 2015 when 251,000 jobs were cut for the age group, according to the Bureau of Labor Statistics.

While the decline was notable, a one-month change hardly makes a trend. In fact, this age group still has the lowest unemployment level among all cohorts, with a 2.7% jobless rate in March unchanged from February. The overall unemployment rate held steady at 3.8% in March.

"This data tends to be volatile monthly. I don't think it's a start of a trend," said Craig Dismuke, chief economist at Vining Sparks. "Broadly speaking, I think the labor market has been very good for people over the age of 55 and 65."

Month-to-month swings can appear large because of the small sample size of the population survey, ZipRecruiter's labor economist Julia Pollak told CNBC.