Grey catbirds are medium-sized songbirds found throughout much of North America. They get their name from their distinctive cat-like meowing call. Grey catbirds build nests in shrubs, thickets and hedge rows, using materials like twigs, grass, leaves and moss. The female grey catbird lays 3-5 eggs per clutch. The eggs are a light blue-green color with reddish-brown speckles.
In this article, we will take an in-depth look at the appearance, size, coloration and other features of grey catbird eggs. We will also discuss how to identify grey catbird eggs and distinguish them from the eggs of other songbirds. By the end, you will have a good understanding of what grey catbird eggs look like.
Appearance and Size
Grey catbird eggs are oval or elliptical in shape. They have a smooth, slightly glossy surface and are mostly pale blue-green in background color. The eggs feature reddish-brown spotting, speckling or blotching distributed fairly evenly over the surface. The markings may be concentrated more at the larger end of the egg.
In terms of size, grey catbird eggs are relatively small, averaging about 24 mm long by 18 mm wide. However, exact size can vary from 20-28 mm long and 15-20 mm wide. The eggs weigh around 3 grams. They are similar in dimensions to the eggs of other mid-sized songbirds like thrushes, vireos and warblers.
Color and Markings
The background color of grey catbird eggs ranges from a pale greenish-blue to a light bluish-green. The exact shade can vary from nest to nest. When newly laid, the eggs may appear more blue but fade slightly over the incubation period.
While the background color is fairly uniform, the spotting pattern is highly variable. The reddish-brown maculation may consist of dots, small speckles, larger blotches or a combination of all three. The markings are distributed across the egg surface but often concentrated more heavily around the large end. Some eggs appear very heavily mottled while others are more sparsely marked with just speckles or dots.
The amount of maculation is thought to be related to the age and health of the female parent. Older, healthier females tend to lay eggs with heavier, denser spotting. Younger females often produce eggs with sparser, lighter spotting. However, even eggs within the same clutch can show variation in markings.
Texture and Shape
Grey catbird egg shells have a smooth, slightly glossy texture. The surface lacks any calcium protrusions or bumps.
In shape, the eggs are short ovoid or elliptical. One end of the egg is more rounded and larger while the opposite end comes to more of a point. The shape is symmetrical rather than elongated or irregular.
Similar Eggs
When trying to identify grey catbird eggs, it helps to rule out any similar appearing eggs of other species. Some potential look-alikes include:
– Northern mockingbird – Very similar in size, shape and color. However, mockingbird eggs are generally a bit greener in tint without the bluish cast of catbird eggs. Markings on mockingbird eggs also tend to be bolder and darker in color.
– Gray catbird – Essentially identical in appearance to grey catbird eggs. Telling the two related species apart by egg alone is extremely difficult and often not reliable. Habitat preferences and geographical range are better indicators.
– American robin – Similar size and shape but robin eggs are a solid light blue without spotting. Some worn robin eggs can show staining however.
– Hermit thrush – Slightly smaller and rounder in shape but fairly similar in color with light blue-green background and reddish-brown blotches.
– Ovenbird – Roughly the same size as catbird eggs but oval rather than elliptical in shape. Background color is pale pinkish-white with extensive dark olive-brown spotting concentrated on the larger end.
Distinguishing grey catbird eggs from the eggs of these other common species comes down to looking at small differences in size, shape, background color and spotting pattern. Being familiar with the species in your area will help narrow it down.
Nesting and Incubation
Grey catbirds build an open cup nest in a shrub or small tree, typically 1-10 feet off the ground. Nests are constructed from a variety of materials including twigs, shredded bark, grasses, leaves, forbs and even paper or plastic. They are lined with finer materials like grass, hair, moss or pine needles.
The female lays one egg per day until the clutch of 3-5 eggs is complete. She does not start full incubation until the last egg is laid. The male may occasionally incubate as well during the female’s brief breaks for feeding.
Incubation lasts 12-14 days before the asynchrounous hatching of the chicks begins. The parents continue tending to the nestlings for another 8-10 days until they fledge. Grey catbirds typically raise 2-3 broods per breeding season across their range.
Range and Habitat
Grey catbirds breed across much of the eastern half of North America. Their breeding range extends across southern Canada from British Columbia to Nova Scotia. In the United States, they nest in appropriate habitat throughout all states east of the Rocky Mountains as well as along the Pacific Coast into Oregon.
These birds favor habitats with dense vegetation, especially early successional areas. Thickets along woodland edges, hedgerows, regenerating clearcuts, abandoned fields, and parks and gardens with shrubby cover all provide prime nesting grounds. They require dense cover for their nests and nearby berry plants are also beneficial.
So when searching for grey catbird nests, be sure to thoroughly check area like overgrown fencerows, brushy field edges or new growth forest stands. Their small but sturdy nests are tucked away securely in the dense vegetation, often close to an outer branch supporting the structure.
Egg-laying Behavior
Grey catbirds demonstrate some interesting egg-laying behaviors shared by many songbird species:
Laying Interval
The female lays one egg per day in the early morning hours until the clutch is complete. This daily laying interval helps ensure the eggs will hatch closely together to reduce differences in chick size and development.
Laying Time
To maximize protection, the female catbird lays her egg quickly, often within just 10 minutes or less. She deposits the egg in the nest cup and leaves soon after to avoid attracting predators.
Nest Sanitation
Right after laying, the female will eat the expelled shell fragments to recoup some of the lost calcium. This helps prevent predators from being alerted by the conspicuous white fragments around the nest.
Egg Rotation
Catbirds frequently rotate their eggs during incubation, using their beaks to roll the eggs over. This may help prevent adhesion to the nest, equalize temperature, and discourage embryonic defects.
Egg Removal
If one egg fails to hatch, the parents may remove it from the nest to prevent it from exploding, spreading bacteria, and attracting predators. Catbirds are tolerant of addled eggs at first but actively eject them as they near the anticipated hatch date.
Stage | Behavior |
---|---|
Laying | One egg per day, takes under 10 minutes |
Incubation | Female incubates for 12-14 days |
Nestlings | Chicks cared for 8-10 days until fledging |
Conclusion
In summary, grey catbird eggs are small elliptical eggs roughly 24 mm by 18 mm in size. They have a pale bluish-green background color with reddish-brown spotting concentrated around the larger end. The amount of markings is quite variable, ranging from sparse speckles to dense blotches.
When identifying unknown eggs, it’s important to pay attention to size, shape, color and spotting details. Grey catbird eggs are most similar to those of other mid-sized songbirds like mockingbirds, thrushes and vireos. Being familiar with the species in your area helps narrow down the possibilities.
Grey catbirds build well-concealed but often frail nests in dense vegetation across much of North America. The female lays one egg per day, incubates for 12-14 days, and cares for the altricial chicks about another week and a half. The parents frequently rotate the eggs during incubation and remove any unhatched eggs prior to anticipated hatching.
Hopefully this provides a good overview of the key physical features and breeding ecology of these common but secretive songbirds. Their beautiful eggs are a special treat to discover hidden away in the greenery of spring and summer.