Sweat Bees (Halictidae) in my garden

Not long ago I thought the only bees which existed in this world were honeybees and bumblebees. Then, when I learned that there were actualy many other species, I looked harder around me and discovered an astonishing variety of bees of many sizes, colours and behaviours, and all that right here, in my backyard! Here are some of them, little sweat bees!

Sweat bee (Lasioglossum Dialictus) on strawberry flower

The smallest bee in my backyard is just 5mm long.  It's a Lasioglossum Dialictus, tiny black sweat bee with metallic green shine, easily mistaken for a fly. I was thrilled when I discovered their nesting colony among the patio bricks in my backyard. The patio is sunny and the soil among the bricks is sandy, making it an ideal site for these ground nesting bees. 

Lasioglossum Dialictus and nest holes

Though solitary, these bees make communal nests, where many bees share one site, while each bee digs her own nesting tunnels to lay eggs (they might even share the tunnels, I'm not sure).  New bees emerge from these eggs early in the spring next year, males first, right around when first dandelions start blooming. I'm trying to find out which native plant could serve as an early nectar source for these bees, but for now, I'm letting dandelions flower, despite the reproachful look I imagine my neighbours might have if they peek over the fence (I try my best not to let them go to seed...)!

Lasioglossum Dialictus males can be seen early in the spring on dandelion flowers, 
most often the only nectar source at this time

As soon as our plum, pear and apple trees start flowering, tiny Lasioglossum females start collecting pollen that will serve as food for developing bee larvae. Since these bees are so small, they have a short flying range, and thus require forage sources to be within a few hundred meters from their nest. 

 Lasioglossum Dialictus female collecting pollen from a plum flower

Lasioglossum Dialictus female, carring a load of pollen 
to her nest hole hidden in the moss between bricks

Another small sweat bee of Lasioglossum spp. I often see in my backyard is Lasioglossum zonulum. This bee is a bit bigger than Lasioglossum Dialictus, but still less than 1 cm long and frequents flowering fruit trees as well as some other small flowers in spring.

  Lasioglossum zonulum on radish flower

Lasioglossum zonulum and honeybee

By the way, according to the report published in the journal Science, wild bees are twice as effective at pollination compared to honey bees! Here is the link for the report:

http://www.sciencemag.org/content/339/6127/1608.abstract?sid=a3bc0103-58a2-490c-ab37-eed6ce4e8933

Sweat bees of Halictus spp. are another species of ground nesting bees that visit our flowering fruit trees in spring.

Halictus rubicundus is about 1 cm long

Green sweat bees (Agapostemon spp.) are the most striking of all sweat bees. Females are solid shiny metallic green in colour, while males have distinct stripes on their abdomens. They are active throughout the year and prefer composite flowers. 

Green Sweat Bee (Agapostemon spp.) female

Green Sweat Bee (Agapostemon spp.) female

Late in the fall, when not much else is flowering, asters are important food source for these, and many other bees.

Green Sweat Bee (Agapostemon spp.) male on Aster spp.

80% of our native wild bees, including the sweat bees, are nesting in the ground and habitat loss is one the major reasons for the decline wild bees seem to be experiencing. That is why I make sure to leave parts of the ground in the sunny sites uncovered (no mulching), I always check the ground for nests before I dig (I dig or disturb the soil rarely anyways). And of course, I never, ever spray any pesticide, organic or non organic, anywhere!

Two queens paid me a visit!

At this time of the year my garden is overflowing with flowering snow crocuses. I imagine they were planted by the English lady who lived in the house some 60 years ago, and spread over the years to cover every corner of the backyard. These crocuses, smaller and wilder than the hybrid ones you can buy at garden centres today, are probably the original wild crocuses native to Europe. 

Honeybee in the sea of snow crocuses.

On a sunny day they attract large number of honeybees, hungry for some fresh pollen and nectar after the long winter.

European honeybee worker collecting pollen. 

Crocuses are also popular with drone flies (Eristalis tenax, introduced from Europe), mimics of honeybees.

The drone fly, a European hoverfly, is widely established in North America.

Now, I don't care much about honeybees or drone flies since they are nowhere to be seen around my flowering fruit trees or blueberry bushes, let alone tomato plants, when they need pollination. From what I've seen, various native bees are the main pollinators in my food garden. Apart from feeding me apples and plums, native bees provide a crucial service,  pollinating native plants so they can set seeds, procreate and provide food for insects, birds and other animals in our ecosystem.

That is why I got excited when I noticed, among all those honeybees, two bumblebee queens, stumbling about from flower to flower, still drowsy and weak from a long winter hibernation. They must have spent the winter buried in the soil somewhere in my backyard, since they were not able to fly for long or far. These bumblebee queens, born at the end of last summer, are the only surviving members of their colonies. As soon as the weather becomes more consistently warm, they will start their own nests. Here they are, searching for nectar to gain much needed energy.

Black-tailed Bumblebee queen (Bombus melanopygus).

Yellow-faced bumblebee queen (Bombus vosnesenskii).

Early flowering plants are of great importance for emerging bumblebee queens. However, not all plants that you see flowering at this time are providing nectar for bees. For instance, daffodils or forsythias have a pretty face, but, much like plastic plants, are totally useless in providing any food for local wildlife. If you live on the Pacific Northwest coast and care about the survival and well-being of our native bumblebees, plant some early flowering and nectar rich plants, like Indian Plum (Oemleria cerasiformis),  a native bush that is in flower in Vancouver right now. Another great native bush getting ready to flower is Red-flowering Currant (Ribes sanguineum). Unlike crocuses, these bushes will also provide nectar for overwintering Anna's hummingbirds, as well as berries which are loved by birds.

One of the two Indian Plums I planted last year is still too small to flower.  
For berries, you must plant both male and female plants.

Red-flowering current flower buds.

There is a new bird in town!

I saw a hawk take down a collared dove today. The dove was searching for food on the ground beneath the old pear tree in my backyard as I came down the path and startled him. He flew up and out in the open and at that moment, while he was just a couple of meters above the the ground, a hawk swooshed down seemingly out of nowhere and pinned him to the ground. The dove did not let out a sound and did not seem to move. There was just a bunch of light grey feathers in the air that silently settled down. It all happened suddenly and not more than five meters from where I was standing, frozen. The hawk looked at me for a few seconds with his piercing yellow eye, then, with some effort, took off with his pray.

And that is how the circle of life demonstrated itself before me today. Nothing unusual there, except that collared doves were not on the hawk's lunch menu until recently.

Collared doves foraging for food in my garden (April 2011)
 

A pair of collared doves appeared in my garden for the first time two years ago. I recognized them right away as they are abundant in Europe where I grew up. I was surprised since I didn't know they lived in Canada too, so I did some research. What I found out is that the species, whose full name is Eurasian collared-dove, was first introduced from Europe into the Bahamas in the 1970s and spread from there to Florida by the 1980s. Well adjusted to living near human habitats, from Florida they rapidly spread throughout North America, which is neatly illustrated on Cornell Lab of Ornithology’s interactive MAP.

The pair of collared doves I saw two years ago might as well have been the first pair that flew in North Vancouver, BC, where I live. This winter I counted 24 collared doves perching on the branches of a big mountain ash tree in my backyard (well, there definitely is one less as of today), so it's safe to say that they are here to stay, and in increasing numbers. Since they mostly feed on seeds and grains, such as millet, sunflower, wheat, and corn (they eat also some berries, as well as invertebrates), I'm sure that they hang around my place because of the big grain silos we have in our neighbourhood. They also spend time around bird feeders, but feed only on the seeds that fall to the ground. According to the Cornell Lab of Ornithology, “studies on interactions between collared doves and other species have not yet shown a negative impact on populations of native birds”, which is somewhat reassuring, since native birds in urban and suburban settings, where collared doves are settling in, are already negatively affected by degrading habitat. And the hawk from the beginning of the story was surely glad to have such big and plump bird for lunch today, and exotic one too!

Cooper's hawk resting in the tree in my backyard

As for me, I don't understand the need for or the reason behind introducing species like house sparrows, starlings or, in this case, collared doves into the "New World". Who would miss a sparrow when they are able to enjoy North America's wonderful diversity of birds? Not me!

 What do you think of the new bird in town?

More info on Eurasian collared-doves:

http://www.allaboutbirds.org/guide/Eurasian_Collared-Dove/id