Monday, May 14, 2018

Bees in Spring 2018

Spring is the best time in Southern Oregon to watch bees! The combination of highly diverse wildflower communities, excellent climatic conditions, and a relative abundance of water culminates to produce a great situation for many species of bees. Without looking up the data, I would bet that the highest diversity of bees can be found in the spring months in Southern Oregon. Not only have I seen more different kinds of bees in the spring than in summer or fall, but there are more native plants in bloom in Southern Oregon than later in the year which offer a diverse nutritional palate.
A honey bee clings to a willow catkin with one leg while grooming the pollen into her pollen baskets. February 22nd.
The earliest blooms in Southern Oregon are found on the trees. Alder, hazel, and willow are some of the first trees to bloom and produce an abundance of pollen for the few bees active at this time as well as a plethora of flies and beetles that feed on pollen. When apiaries or the odd feral honey bee colony are located near any of these trees, often near bodies of water, they delight in the abundant pollen on warm sunny days. Few native bees are active in January or February when the earliest blossoms appear, but I saw Andrena and a few bumble bee queens foraging on willow catkins in February this year.
A mating pair of Ceratina on pear blossoms. April.
Southern Oregon in April is host to billions of pear blossoms. Pear orchards are fairly commonplace around Medford, though many have been sold and turned into housing developments or hemp farms, much to the dismay of bees and other pollinators. Pear growers use honey bees to pollinate their trees, but the beekeepers make a fraction of what they are paid per hive in the almond orchards in California. Where almond growers may pay up to $200 per honey bee hive in the almond orchards of the Central Valley in California, pear growers rent less hives and might pay up to $40 per hive. This is probably because almonds bloom much earlier than pears, a time when few native pollinators are active, and almonds are currently much more valuable than pears. Consider the cost of pears compared to the cost of almonds next time you go grocery shopping.
A mating pair of Ceratina on pear blossoms
The pear orchards of Southern Oregon, at least the ones I have been in, are surrounded by a lot of natural landscapes and filled with flowering weeds. Whereas almonds are harvested by shaking the trees and then raked from the ground, the floor of the almond orchards needs to be bare or mowed. Pears are not collected this way, so the ground beneath the trees is sometimes overgrown with weeds. This offers a lot of resources for native and managed bees alike.
Osmia on a crab apple blossom. May.
Apple blossoms follow the pears. I am not sure there are many apple orchards in Southern Oregon, but they are grown as ornamental trees and personal orchards. Mason bees, Osmia spp., are sometimes managed for pollination of spring tree crops including almonds. Unlike honey bees, each female creates her own nest and does not live socially. In fact, most female native bees fulfill the role of both queen and worker. Osmia are called mason bees because they use mud to build the cell walls and partition cells in their nests (preexisting linear tunnels, usually in wood).
Nomada on a crab apple blossom
Peculiar, wasp-like, and fascinating. That is how I like to introduce the cuckoo bees. As the common name implies, they steal the nests of other bees. Unlike the birds of the similar name, cuckoo bees lay an egg in the cell of a host bee, such as Andrena or Halictus, and the cuckoo bee larvae usually kills the host larvae and develops on the food (a ball of pollen) collected by the host bee. Since the cuckoo bees steal nests from other bees, they don't create nests themselves. Since the nest they steal is provisioned by the host, they have no need to collect pollen, and thus they don't have pollen collecting hairs on their bodies.
Nomada female searching for host bee burrows
Cuckoo bees in the genus Nomada are usually black, yellow, red, or a combination of those colors. I was lucky to see a few red and black females hovering just inches from the ground recently. They were seeking host nests, probably Andrena or Halictus which nest in soil. Nomada females find Andrena nests by olfactory cues (Cane 1983).
Anthophora female on Phacelia tanacetifolia. May.
Phacelia tanacetifolia, or lacy phacelia, is a member of the Boraginaceae, native to California and possibly Oregon. It is more commonly available as seed and usually grown as a cover crop, ornamental, or sometimes specifically for bee forage. It doesn't let down, it is a great bee plant. Bees of all shapes and sizes, as well as a variety of other types of pollinators, are attracted to the blue scorpioid inflorescences.
Anthophora female on Phacelia tanacetifolia
I recently had the opportunity to observe bees visiting a large planting of P. tanacetifolia at Easy Valley Farm in Rogue River, OR. One of the more conspicuous types of bees were the large and fast digger bees. Anthophora is a common and widespread genus with some species remaining active from spring to fall. While some solitary bees only have a single generation each year, some species have two or multiple generations. At least some if not most species of Anthophora produce offspring all year, with the last generation of the year overwintering as prepupae within underground nests.
Halictus on Phacelia tanacetifolia
Sweat bees, more accurately known as halictid bees since not all species are attracted to sweat, are very active in spring and summer. They vary widely in size and nesting habits, and are very widespread and speciose.
Bombus vosnesenskii clinging to an Anchusa azurea blossom
An Old World member of the Boraginaceae, Anchusa azurea is found in my garden and in those fortunate enough to have acquired it from seed. It is like a large forget-me-not, and is very attractive to bumble bees and honey bees. I photographed an odd flower with only four lobes, most have five, with a bumble bee clinging to it early one morning. This bumble either was caught in the cold and unable to return home, or wanted an early start.
Iris chrysophylla with a bumble bee
Iris chrysophylla, yellowleaf iris, is a dryland iris found among grasses in mixed coniferous forest clearings and edges. It blooms profusely in mid spring over a long period in Southern Oregon. Various bees visit the flowers, including mason bees, halictid bees, and bumble bees. Though it is visited by various bees, I do not typically see a lot of bees visiting the flowers even where it is blooming in large masses.
Bombus diving for nectar on Iris chrysophylla
Iris flowers, as well as a few other Iridaceae relatives found around the world (i.e. Hermodactylus, Moraea), are complex and peculiar. To oversimplify, each single flower is divided into three ports of access for bees to enter seeking nectar. Pollen is typically deposited onto the back of the bee, but only if it enters the correct way. Bumble bees have very long tongues and are able to circumvent the reproductive structures and access the nectar from the side.
A honey bee forages for nectar on Calochortus tolmiei
While Iris chrysophylla grows from a short rhizome, Calochortus tolmiei grows from a bulb. Calochortus is only found in the New World and is very unlike other New World bulbs in flower structure. C. tolmiei is one of a handful of species with peculiar hairs on the petals, likely an adaptation to prevent inefficient pollinators from stealing the nectar. Nectar is excreted from colored patches at the base of the petals, and the hairs force the bee to rub against the anthers to access it.
Calochortus tolmiei and a honey bee fleeing from a camera that came too close for comfort.