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Science Insider

Feeding Pollen Might Not Be as Useful as You Think

- December 1, 2020 - Alison McAfee - (excerpt)

protein supplement bees

It might make us feel like good beekeepers, but fall protein supplementation doesn’t produce more winter bees 

Many beekeepers do it. Local bee clubs suggest it to their members, and some old-timers have done it for decades. Even some apiculture authorities suggest it. But it might not be providing our colonies with the benefits that we think it is.

Feeding pollen or pollen substitute in the fall is so routine in some spheres that its utility doesn’t seem to be questioned. This protein boost, says conventional wisdom, promotes brood rearing at a time when pollen availability is dwindling. More fall brood reared by well-fed nurses means more fat winter bees, and more fat winter bees means there’s a higher likelihood of the colony coming out in good shape in the spring. Right?

Actually, research suggests otherwise. Dr. Heather Mattila, an associate professor of Biological Sciences at Wellesley College, Massachusetts, conducted a sequence of studies, starting in 2002, showing that fall pollen feeding has no impact on the winter bee population size nor their longevity.

Mattila, who was studying in Dr. Gard Otis’ laboratory in Guelph, Ontario at the time, fed five colonies supplemental pollen patties, giving them one pollen patty a week for four weeks between September and October. For five other colonies she restricted pollen during the same period using pollen traps, and she applied no treatment to five more.1

Mattila carefully measured how fat the winter bees really were by recording their dry mass. She tediously marked cohorts of newly emerged bees with colored number tags, and recorded who was left alive in the colony at different time points to determine longevity. And she painstakingly measured capped brood area — data which she incorporated into a model to estimate adult population size — every twelve days until brood rearing ceased, and again when rearing commenced in the spring.

“In full-sized, established colonies, providing a pollen or pollen substitute in the fall promoted a short-term boost in brood rearing,” says Mattila. But, she explains, “This brood-rearing boost delayed the transition in colonies to a population of long-lived winter bees, and didn’t translate into improvements for the winter bee population.”

Pollen supplementation indeed had the desired effect of nourishing the nurse bees and supporting the colonies’ ability to rear brood. It just wasn’t the right type. Despite the onset of fall outdoors, those bees were summer bees, and soon died off to leave a similar population of winter bees compared to the other colonies.

“Evidently,” Mattila and Otis write in their research article, published in The Canadian Entomologist,1 “none of the extra pollen provided to colonies was invested in enhancing the quality of winter bees that colonies reared, nor did the performance of winter bees suffer from a restricted supply of pollen during the fall.”

“I was surprised that [Mattila] found no positive effect of feeding pollen supplements,” says Heather Higo, a lifelong beekeeper and bee researcher in Langley, British Columbia — a response echoed by many beekeepers. “In this area, because we sometimes have long, mild fall weather, I think we are more prone to feed pollen supplements in the fall as well as spring to ensure we get well-nourished nurses.”

Ontario and BC do have very different climates — Ontario winters are colder and longer — but average temperatures in September through November are surprisingly similar. Mattila expects that, although her work was conducted in Guelph, Ontario, results would be comparable in other Canadian provinces and the northern U.S.

“I don’t feel I can make concrete recommendations to beekeepers about the utility of feeding in the fall,” says Mattila. “It is possible that the effects of a late-season brood rearing boost would be more advantageous in smaller colonies. However, there is no information available about whether fall feeding would help winter bee populations in newer colonies in a way that is different from the larger colonies we used in our study.”

In a second research article, Mattila and Otis show that pollen availability is actually an important cue that controls the timing of rearing winter bees, which may explain why pollen feeding did not improve the quality of winter bees.2 When they fed colonies pollen patties for different lengths of time into the fall, they found that colonies whose pollen supply dwindled earlier had a correspondingly early onset of rearing winter bees. Conversely, those receiving extended pollen supplementation into the fall delayed their winter bee rearing. But all groups still produced similar numbers of winter bees, in the end.

Feeding pollen in the fall does not “fatten up” winter bees, as I have seen written numerous times online. Yes, winter bees are fat, in a sense — they are indeed heavier than summer bees, with higher levels of proteins, fats, and sugars in their blood and swollen glands. But that fatness isn’t facilitated by feeding colonies extra pollen — instead, feeding pollen just puts off fat-bee-production until they finally get the signal that pollen is running out. And that delay doesn’t have a significant impact on the strength of the colonies at the beginning of spring, either.

But I still hear fall feeding come up as standard colony management procedure, particularly within bee clubs. The practice is encouraged in the “First Year Beekeeper” guide on a prominent beekeeping blog. And the Atlantic Tech Transfer Team recommends feeding pollen in the fall if it looks like the colony has fewer than 3-6 frames of pollen going into winter.

“I was advised years ago to feed pollen in the fall if you plan to use your bees early the following spring to make nucs or early splits,” says Higo. “The thought was that it would act as insurance that the overwintering bees are strong and well able to rear plenty of brood early in the year.”

Higo normally feeds a pollen patty in September, and then not again until February. She notes that the speed at which the patty is consumed in September, even if the bees don’t necessarily need the protein, can also serve as a useful diagnostic. “If it doesn’t get eaten quickly, that can be a sign that the colony is not strong or has a queen issue that requires more investigation,” she says.

Well-known management guides, like Canadian Best Management Practices for Honey Bee Health (commissioned by Agriculture and Agri-Food Canada), the Beekeeping Calendar for the Northeast (from Cornell University), and Best Management Practices for Honey Bee Health (from the Honey Bee Health Coalition), don’t mention fall pollen feeding at all. This, while being, strictly speaking, aligned with Mattila’s work, may add to the confusion when new beekeepers are trying to figure out what to do.

“Beekeepers generally want the best for their best, and upon hearing success with a management practice, they may be willing to try it,” says Kerry Clark, president of the BC Honey Producers’ Association and long-time beekeeper in the Peace region. But Clark cautions that feeding pollen comes with risks, regardless of the time of year.

“For pollen collected from other hives,” he says, “the freedom from pathogens is critical. Trials done in Saskatchewan showed that colonies fed pollen did worse than those unfed, owing to the loss of brood  ….