Dead bees along the outside of your house or building can be signs that a hive of bees is planning on moving in or has already moved in and are living in or near the wall, eave or structure. An established hive typically has 2,000 to 20,000 bees). In some cases upon observation you may also see dead or what look like sick bees on the ground or being carried out by one or two bees and dropped somewhere, or just the occasional bee stumbling out and dying.
Causes for dead bees outside of the house may include any of the following:
A bee hive has recently split causing the swarm to travel and moved into the location. During the process, old or weak bees die along the way or sometime shortly after they arrive. These are often the dead bees you are seeing.
Another cause for dead bees outside of the house or structure is that the beehive may have a disease which is affecting them, causing a percentage of them to die outside the house. Dead bees outside on the ground almost never means the problem will resolve itself.
You might find dead bees near the front door of a house or the back porch. This is often caused by an automated porch light that comes on before dark, becoming brighter as the sun sets. A such, either this light is in the bees flight path on the way home, or a large tree is nearby with a lot of bee activity and at evening are drawn to your porch light loosing there way home; after which they buzz around it tell exhausted then die or appear lethargic by the porch. This is typically a sign that there is a bee hive attached to your house or nearby.
A house or building typically may attract a beehive every 30 years or so; however if the building has a history of bee problems, bees can appear every year. A reason for dead bees outside of the house is that when the hive and honeycombs are not removed the smell can attract bees regularly to that spot or a spot nearby. This also tends to attracted rodents, carpet beetles, and other critters.
Removing a nest can be a critical part of solving a bee problem (bees in wall).
An unlikely cause for dead bees near the house or along the side of a structure may be caused by a recent fight with another beehive trying to steal honey. This can happen more often in winter when honey is scarce.