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Purple Martin Twilight
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Chronological Colony Life
Usually the first birds to return are the older ASY birds. These birds are often established in a site somewhere and, if successful with nesting last season, will usually return to that site to do their nesting each year. This is known as 'site fidelity'. Since they have successfully raised young at that site before, they feel safe enough to return to that same site to do it again. Although not always, the older males are usually the ones to arrive first. These early arrivals are usually known as 'scouts'. Because of the nature of martins to show up at a site for a period of time, then disappear for days, it was once thought that these birds arrived first to check the site out and then returned for the rest of the flock, but this 'longtime myth' has been proven wrong. Scouts are nothing more than the first birds to arrive for the spring migration and the other birds simply arrive when they are ready.
Once these early birds arrive, they set about getting to know the area again and simply lounge around until more birds arrive. This is why you may see them for a short while and then they disappear for long periods of time, even days. They are in no hurry to do anything. Martins are superb fliers and spend many hours on the wing finding food or just plain enjoying life.
Once the females start arriving, the males begin selecting as many adjacent compartments in the site as they can successfully defend. (Known as 'male porch domination'). This is done with the intent of possibly attracting more than one female to mate with. They then seek out the females, attempting to court them and persuade them to set up house keeping with them. Again, the females have just arrived and are in no hurry to settle down. This is when the males are most vocal, chasing after and courting the females, insisting that they investigate the cavities that they have claimed. An interesting point here, females don't pick the first male that comes along. Instead, they investigate the cavities each has chosen and if they like the cavity, then they will stay with the male that owns that cavity. This is another reason why it's advantageous for a male to acquire and defend more than one cavity. Often, if they survive the migration, the same pairs will mate each year providing he has the same good cavity. Once she's made her decision, the pair will strengthen their bonds, the male following her everywhere she goes, protecting her from other males while at the same time, trying to attract more females to his other cavities if he possesses them.
About 4 to 6 weeks after the ASY birds have arrived, the SY birds will begin filtering in. These are the birds that were born the previous year and have not yet nested or even selected a site. Since they are not already established in a 'site', they begin looking for a place to start a home. These are the birds that are usually attracted to new sites to start new colonies. Upon first arriving in an area, they also are in no hurry to start nest building or egg laying. They instead, flirt around the different homes they find, investigating all available ones until they find something that they consider interesting. This is why it's imperative that new potential landlords make their sites as appealing as possible.
One unusual thing the established males do is attempt to attract other males to the site. This is done with hopes of breeding with any females that they in turn may attract. (This is known as forced pair copulation). This is especially done with the SY birds, since they have not nested yet and may not know how to defend their females. All the time they are doing this, they are trying to defend all the holes in their immediate territory for more possible females. If the young males do decide to stay, they in turn will try to attract other females. This is one of the most active times around the site and a lot of noisy chattering, fluttering and squabbling will take place. Plus, it's one of the ways a site will grow.
After a few weeks of lounging around, the older birds will settle down and nest building will start. Sometimes this nest building begins even before the SY birds begin arriving and thus, makes the year last longer for the landlord. Nesting may be spread out as much as a month or two because of the different ages of the birds. Both birds will make nesting material gathering flights, but it is usually the female that ends up doing most of the work, refining the nest to her liking. The male will usually make flights with her to hurry her on and to also protect her from other males while she is on the ground. This is when she is most vulnerable against the forced pair copulation from other males. This nest building usually lasts from about 3 days to 2 weeks for each pair. The material they gather may vary from grasses, pine needles, (pine straw), sticks, small stones, mud and fresh green leaves. Even things such as gum wrappers and cigarette butts may be found. On smaller compartments, the mud is usually used to make a dam in the front of the nest leading up to the entrance hole. Most of the time, these mud dams are built in the smaller nesting compartments and is thought to be protection from the elements. Mud is seldom used in the larger gourds and deeper compartments. The reason for the green leaves is not actually known, but they are believed to keep the eggs moist and usually cover the eggs with them when they leave to forage for food. The birds will replenish these leaves from time to time.
In the back of this nest, the female makes a small depression or bowl, and when nest building is complete, it's here she will place, depending on her age, anywhere from 2 to 7 soft white eggs. The SY pair will usually lay smaller clutches of about 3 or 4 eggs while the ASY pair will often lay 4 or 6 and sometimes even 7 if the compartment is large enough.
Not surprisingly there is a second factor that will sometimes dictate how many eggs are laid. If the nesting cavity is larger in size, such as a 7" x 7" x 10" cavity or a 10" diameter gourd versus a 6" x 6" x 6" nesting cavity, the average number of eggs laid will surprisingly increase in number. Apparently, with the extra room, they will lay more eggs. It's very common for mature birds to lay 7 eggs if there is room for them to do so, however there also has to be abundant food available to feed the young.
Once egg laying begins, eggs are laid at the rate of one per day, usually in the morning around daylight or shortly after. This is how a landlord, doing nest checks at 4 or 5 day intervals and keeping good records, can tell when egg laying started and thus approximate when hatching will begin. Actual incubation begins with the laying of the next to the last egg. The incubation stage of the nesting period will last for about 16 to 18 days with the female doing most of the incubation. During this period, the males will simply sit around or fly off to gallivant on the breezes of the day.
At the end of this incubation period, all the eggs will hatch within a day or two of each other. Young martins are born featherless, a term known as Altricial. (Birds born with feathers are known as Precocial). Once all young are hatched, the brooding stage begins and will last for about 28 to 30 days after which time the young will fledge. This is probably the busiest time for the adult martins, having to gather enough food to keep the young fed. Trip after trip has to be made to supply the ever hungry, growing fledglings with enough food so they will grow into birds that are ready to fly within one months time. About a week to 10 days before the young fledge, they can be seen poking their heads out of the compartment entrance hole, taking stock of the neighborhood while waiting for the parent birds to return with more food. This is an anxious time in the colony. Predator attacks become more prevalent when there are a lot of young present. It's a must to have predator guards in place during incubation and brooding times. Many predators would love to get at the eggs or young martins and make a meal of them. This is an especially good time for the landlord to make daily walk-unders in his colony, checking out the ground and making sure that all is good in his martin housing.
Since all birds don't start nesting at the same time, this activity period will be spread out over about 4 to 8 weeks. Some compartments will be busy while others will not. But, once eggs are hatched and young are present, the activity level for that nest increases greatly. Regular nest checks by the "Landlord" will keep him/her fully informed as to the condition of the site and the young in it.
At about three days before the young fledge, they are about the same size or even larger than the adults. At this time, they're probably too heavy to make that first successful flight. The parent birds seem to know this and will stop feeding them. This causes the young to lose some weight, thus enabling those first crucial flights to be successful. The parent birds can be seen trying to encourage the young to come out of the compartments and fly. With enough observation, a landlord might even catch sight of a parent actually pulling a young one out of the entrance hole, trying to get them to take that first leap.
Upon exiting the nest, the young will take off with much excitement. The parents will often chase and harass the young, screaming at them, seemingly scaring them into flight. This first flight is a critical one. They have to learn to fly, and they have to learn to fly well, quickly. Their life depends on it. There are many predators that are waiting on the young and they have to be able to fly very well in order to evade these predators.
Once fledged, the young will practice flying, landing and taking off again, returning to the site occasionally for a rest and they may even spend a night or two in the compartment, but they will not stay long. For about a week, the young will practice flying while still begging for food from the parent birds. Often, they can be seen on nearby power lines or open trees, begging for food from the parents and waiting for the parents to feed them. But, as nature will have it, all good things must come to an end and the young have to start feeding themselves. They will now have to put their practice flights to use. They will start hanging out with the adult birds, learning how to feed themselves and beginning to enjoy the start of their lives, investigating everything that is around them. They will visit any and all houses that they find in the area, making mental notes of the area where they were born. Although the majority of these young will not return to the site of their birth, most will usually stay within a 25 to 50 mile radius. This is nature's way of keeping inbreeding at a minimum. This is why your housing should be left up until the birds have gone for the summer. These practice flights of other young will include investigating your house and just maybe they'll return to your house next year.
After a couple of weeks of this, the entire flock will now start gathering in 'communal staging areas'. This is an area where birds from the general area will gather, readying themselves for the long and arduous flight south to their wintering quarters in South America. The groups will be small at first, but as more birds hatch and join in, they will grow in size. Although not always, these gatherings are usually around areas where there is fresh water present. They need to drink, and water usually harbors thousands of insects, something they need to gain the energy that is required to make the long trip south. Except for a few late nesting pairs, it's at this time that the small individual sites will become void of birds. This is a sad time for the landlord. Their birds are leaving for another long winter. But, we as landlords shouldn't be sad. This is what our hard fought efforts were all about. To attract birds, have them successfully raise young, and then watch them fly away into the sunset. A cycle that is repeated year after year at site after site.
It's now late summer, the sun is retreating lower in the sky, the weather is getting cooler, anticipation of fall and winter is running high. It is now time to take the housing down, clean it out and fix any and all problems with it. Might even need to paint a gourd or two. We've done everything we were told to do and we successfully fledged some baby martins. Now, all we have to do is wait for spring to do it all over again, and that's just around the corner.
Some questions and some possible answers...most are common occurrences around a purple martin colony.
I've been told that I shouldn't bother the birds during nesting or they will leave...
Not so. That was your mother's way of telling you to leave the birds alone when you were a child, otherwise, not knowing any better, we would have disrupted the nest. However, it's a proven fact that when regular nest checks are done on a purple martin colony, more and healthier young are produced than at one that has been left to its own accord. The landlord that is involved has a much better handle on the activities or problems that may arise in the colony. With these regular nest checks, good records are able to be kept, and the landlord is then able to give immediate attention to problems and correct them before anything detrimental happens to the site. Landlords that are out, around and under their housing every day will get to be known by their birds and the birds will quickly begin to trust them. Soon, their presence is practically ignored as the martins go about their daily activities. Contrary to common belief, the martins will not mind at all if you temporarily invade their nests. In fact, if done right, after some time, some of them won't even get off the nest but will stay there and ride the housing down...
May 10th, 2012
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