For many of us, little brown birds can be exasperating fellows. They’re small, they never stand still, they either all look the same or look like nothing you’ve ever seen. The generally don’t look like anything in the field guide too. Then there’s the Brown Thornbill/Striated Thornbill thing if you live around Sydney. The “thing” is what seems to be their great similarity when viewed through binoculars, despite the vast differences which are portrayed in the field guide!

It all comes down to experience and observation, meaning that you have to take whatever opportunities you can to observe these two species side by side.

The problem here is that Brown Thornbills are mid-storey/shrub layer foragers and Striated Thornbills are canopy or treetop foragers. How do we get to compare the two when they live so far apart? Let’s face it, we so seldom get the chance to even find a Striated Thornbill as they’re so tiny and never come down from the tree tops.

Separate species, separate lives

The answer can be found if we follow the lives of these tiny insectivorous birds. Brown Thornbills are monogamous pair breeders: a fairly unique arrangement among the cooperative breeding thornbill clade. This is why you seldom see Brown Thornbills in any more than pairs. Of course, around breeding season you will see them feeding their young, who will remain in their parent’s territory until they’re of an age when they can disperse, but this is not the norm.

For Striated Thornbills it’s a very different story: these birds move around larger territories in extended family groups of around, and sometimes more than, 30 birds. When breeding season comes these tiny thornbills pair up and, in the company of a couple of younger “unmarried” birds, will construct a nest and raise their young cooperatively. By “cooperative” we mean that the “unmarried” birds – frequently the previous year’s offspring – assist the breeding pair in raising their offspring. Families build their nests in trees around 50 to 80 metres apart, depending upon the structure of the forest. If a family fails in its breeding attempt, it will join up with its neighbours and assist them with raising their family. When the entire process is complete, the super extended family joins together again and every member of the flock feeds any young which still might be begging for a morsel. The time of year when this takes place around Sydney is from mid August to late October.

Now’s the time to make comparisons

It’s of great use to little brown bird enthusiasts that breeding season is the time of year the Striated Thornbills greatly diversify in terms of where they forage. Right now you will find Striated Thornbills foraging among the understory shrubbery, mid-story and canopy layer, so it’s an excellent time to see these birds down low very frequently. This is a time when Brown and Striated Thornbills come into conflict and I’ll have more on this in a coming post. This also gives us the opportunity to make the comparisons which will help us to really improve our ID skills with these two species.

Like all of these things, it’s easy when you know how and you also know the pitfalls in identifying these birds. Let’s go through them . . .

Rules for observing Little Brown Birds

First up and most importantly: Don’t get fooled by the similarities. Most birders who struggle with little brown birds get caught up focussing on the similarities. Here, we’re going to learn about the immediately apparent differences which will aid identification. We’ll consider these in the light of some of the pitfalls which invariably crop up in the field.

The following two images aren’t meant to be works of art: they’re meant to clearly define the diagnostic features of these two species. To serve as an indicator of what to focus on in the field. If you look for these features when you see these birds, you’ll notice that they’re immediately obvious.

1. Chest markings

Determine if your thornbill has striations or “arrow heads”. There are clear differences in the chest markings of Brown Thornbills and Striated Thornbills. The Brown Thornbill’s chest markings are clearly more like arrowheads in shape. The pitfall is wet birds. If a Striated Thornbill is damp from, getting about in wet foliage, its chest markings may appear to be more like arrowheads. If your bird is wet, move onto the next easy field marks . . .

2. Crown colouration

These two thornbill species are really easy to split by crown and facial plumage. The Brown Thornbill has a plain face and cap, with a buff-rufous frons (forehead). Its facial markings are fine and not so striking. The Striated Thornbill has an obvious tan-brown cap with tiny white striations through it. The dark striations on its face are more prominent.

3. General colouration

The Brown Thornbill is generally brown or greyish in overall appearance, whilst the Striated Thornbill has an obvious yellow tinge to its body. The pitfall can be poor lighting and if this is the case, move on to the next easy diagnostic feature . . .

4. Eye size and colour

The eye of the Brown Thornbill appears to be very large, whereas the eye size of the Striated Thornbill tends to appear to be of what we consider normal proportions. If light permits, you will note that the Brown Thornbill’s eye is red-brown and the Striated Thornbill’s eye is very dark or, in direct light, pale grey.

Sealing the ID – experience is the key

Generally the path to identification is to pick one of these features and then use a second one to make a positive identification. However you will note that these are all comparative features and that is the point of this post. You need to get experience comparing these two species side by side or at least see them both in the same morning’s birding. A few encounters with these delightful small birds will give you the opportunities to use the tools to put away your ID issues with both of them and enhance your day in the beautiful Sydney bush.

We’re going to be looking at the lives of these birds in greater detail over coming weeks: what they can tell us about the environment, how they contribute to healthy ecologies and they respond to changes which humans impose on their environment. They’re exciting stories which take us into the heart of what the study of birds is about, understanding what you’re looking at in the field or simply enjoying your birding more. They also help to inform us about improving the way we manage and relate to the environment. There’s really no end to the fascination out there for those who are fortunate enough to love birds and nature and these little brown birds are a great entrée to much of this.

Until next time . . . Happy Birding!

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Birding by Ricki