The Northern Mockingbird (Mimus polyglottos) is a medium-sized songbird found across much of the United States and parts of Mexico and Canada. Known for its complex and melodious song, the Northern Mockingbird plays an important ecological role as an insect eater and is the state bird of 5 different states.
An interesting aspect of the Northern Mockingbird’s life history is its mating behavior. Mockingbirds form monogamous pair bonds during the breeding season and both males and females participate in mate selection. The mating rituals of the Northern Mockingbird involve elaborate courtship displays by males, including visual displays, vocalizations, and offering food gifts to prospective mates. If a female accepts a male’s advances, the pair will mate and cooperate to build a nest, incubate eggs, and care for the young.
In this article, we will take a closer look at the fascinating mating behaviors of the Northern Mockingbird, including courtship displays, mate selection, pair bonding habits, nest building, and parental care duties. Understanding how this iconic songbird attracts mates and raises its young provides insight into its natural history and ecology.
Courtship Displays
The mating season for Northern Mockingbirds occurs during the spring and summer months of March through August. As the breeding season approaches, male mockingbirds begin establishing and vigorously defending nesting territories. An important part of territory defense is the performance of courtship displays to attract potential mates.
Male mockingbirds engage in elaborate visual displays that showcase their appearance and agility. A common display involves the male perching in an exposed area and slowly opening and closing his wings in a “wing waving” motion to highlight his white wing patches. He may fan his tail or puff up his body feathers to appear larger and more impressive. The male will sometimes rapidly flutter his wings or spread his tail during these performances.
Vocal displays are another key component of mockingbird courtship. Male mockingbirds sing complex and melodic songs to advertise their nesting sites and attract mates. Different males have their own repertoires of song types that they mix and match while singing. The songs increase in intensity as the breeding season progresses. Unmated males may sing almost continuously throughout the day during peak mating time. In addition to full songs, males give shorter call notes and sometimes mimic the sounds of other birds when displaying.
Mockingbirds are also known for their “flight song” display, in which the male sings while flying high into the air and back down to a perch. Alternating wing beats and silence during these flight songs highlights the male’s singing skill. This challenging aerobatic display demonstrates a male’s physical fitness.
Food gifts are another courtship behavior of male mockingbirds. A male will forage for food items such as insects, fruit, or seeds and present them to a female he is attempting to impress. If the female accepts these offerings, she sometimes bends over and exposes the feathers on her back in a begging display to request additional food gifts from the male. This shows her interest in the male as a potential mate.
Mate Selection
Female Northern Mockingbirds play an active role in evaluating and choosing a mate from among available males in their habitat during the breeding season. Females assess the songs, visual displays, and courtship feeding efforts of males when deciding whether to select a mate.
Research suggests that female mockingbirds prefer males that demonstrate greater song versatility, complexity, and performance consistency. A male capable of singing many different song types for long periods likely has good stamina and cognitive skills that could indicate genetic fitness. Males with the most elaborate song repertoires and intense singing behaviors tend to attract mates most successfully.
The vigor and persistence of a male’s visual displays also influences female choice. Females likely prefer males that have brighter plumage, larger size, and better flight maneuverability. A male that can sustain physically demanding display flights may represent a higher quality mate.
Females also pay attention to the nests males build and the food gifts they offer when weighing mate choices. Males that construct more robust nests and provide larger or more frequent food items show evidence of parenting ability. Since mockingbirds exhibit biparental care, choosing a male who exhibits nesting skill and food provisioning interest can benefit the female’s reproductive success.
While female mockingbirds express preferences during mate choice, some females may pair with less desirable males if there is intense competition for high-quality mates. Younger females in particular often end up mating with older males that are better able to acquire high-quality nesting sites. But in general, exercising choice allows female mockingbirds to select mates with traits that indicate better potential benefits for their offspring.
Pair Bonding
Once a female mockingbird has chosen a mate, the pair forms a monogamous bond for the remainder of the breeding season. However, mockingbirds usually pick a new mate in subsequent years rather than maintaining long-term pair bonds across different seasons.
Cooperation between the mated male and female is important for increasing reproductive success. The male continues courtship feeding of the female while they work together to build a nest. The female mockingbird does most of the actual nest construction, though the male will sometimes offer sticks or other nesting materials.
The male will also stand guard and chase away intruders or predators that get too close to the nest site while the female is incubating the eggs. Both parents then share duties of bringing food to the hatchlings and fledglings. Having two parents invest significant effort improves the survival chances of their offspring.
Even as a pair, mockingbirds maintain separate foraging and roosting sites outside of the nesting area. But the male continues defending the nesting territory from trespassing mockingbirds throughout the breeding season. Both mates are highly aggressive toward intruders.
Staying close to the nesting site and frequently returning with food enables the male and female mockingbirds to confirm their mates are investing appropriate care in the young. Male mockingbirds are occasionally documented destroying nests and harming offspring if they suspect their mate has been unfaithful. Maintaining the pair bond through cooperative breeding is therefore important for the mockingbirds’ reproductive investment.
Nest Building
About a week after pair formation, the female Northern Mockingbird begins building a nest in preparation for egg laying. Mockingbird nests are bulky, cup-shaped structures composed of an outer layer of sticks with an inner lining of grass, bark, leaves, moss, and sometimes hair or trash.
Nests are usually 3-10 inches across and 3-6 inches tall. The female does most of the construction work, though the male may contribute some material. She builds the nest over a period of 3-5 days spending 2-4 hours per day collecting materials and weaving them into shape.
Ideal nesting spots provide a foundation of firm horizontal branches or forks in a bush or tree. Mockingbird nests are typically found 3-10 feet above ground in the cover of dense shrubbery. This offers concealment from predators while still allowing the parents to monitor the surroundings.
The female mockingbird secures the nest to its base by firmly weaving anchor materials like rootlets or twigs through the outer branches. She then uses her beak to tightly interlace the softer lining materials into a compact, weather resistant cup shape. The deep, thick-walled interior provides insulation and safely cradles the eggs.
Many female mockingbirds build between one to five nests per breeding season and choose the one they judge to be of the highest quality for laying eggs. More elaborate nests may represent greater female investment. Building multiple nests also serves as a decoy to distract predators from the active nest site. The additional unused nests are left intact by the mockingbirds.
Egg Laying and Incubation
Once she completes nest building, the female Northern Mockingbird lays a clutch of 3-5 pale blue or green eggs with small brown, red, or purple spots. The eggs measure about .8 to 1 inch long. The female produces one egg per day over a span of several days until the clutch is complete.
The female mockingbird incubates the eggs by herself, though the male will briefly take over incubation duties to allow the female to leave the nest to forage periodically. Incubation lasts 12-14 days before the eggs begin to hatch. The altricial hatchlings are naked, blind, and completely dependent on parental care.
To warm the eggs, the incubating parent (usually the female) presses the eggs against her brood patch, an area of featherless skin on the belly that allow efficient heat transfer. The female attentively turns the eggs during incubation to ensure even warming. Both parents develop brood patches prior to nesting.
Incubating mockingbirds are highly defensive of the nest and may attack intruders or dive-bomb predators that get close, including humans, cats, and hawks. However, they usually flee if a major threat like a human climbs the nest tree, only returning when the danger passes. This helps ensure their survival so they can continue caring for the current brood or produce another clutch if the first fails.
Hatching and Nestling Care
The altricial Northern Mockingbird hatchlings are born with eyes closed and no downy feathers. Their pink skin is visible through their sparse, pale gray protofeathers. They weigh just a few grams at hatching and are totally reliant on their parents for warmth, shelter, and food.
For the first few days, the nestlings are brooded for long periods by the female mockingbird. Her body heat keeps the hatchlings warm as their feather covering and internal temperature regulation slowly develop. The male also broods the young for short periods to give the female breaks.
As they grow a layer of gray downy feathers within a week, the nestlings can maintain their body heat better. At this stage, both parents take turns bringing the hatchlings food. Nestlings beg for food with loud peeping and gaping of their mouths. Typical diet items delivered by the parents include insects, spiders, earthworms, snails, fruit, berries, seeds, and minced lizards or nestling rodents.
The hatchlings grow quickly and are ready to leave the nest at 10-14 days old. Towards fledging age, the nestlings exercise their wings frequently inside the nest and stand on the rim peering out in preparation for their first flight. They will remain dependent on parental care for 2-4 more weeks after fledging while they refine their flight skills and foraging abilities.
Fledging and Post-Fledging Care
At around 10-14 days old, the Northern Mockingbird nestlings are ready to take their first flight and leave the nest, a process called fledging. The gray fledglings have fully feathered bodies and short tails at this stage. Their flight feathers are about 2/3rds of full adult size.
Fledging often occurs in the morning after sunrise when winds are light. The first flight of mockingbird fledglings is usually clumsy and short, often landing close to the nest in a nearby shrub. Once airborne, the entire brood will typically fledge within 1-2 days.
While fledged mockingbirds can flutter upward to low branches, their initial flights are not strong enough to reach high perches. The parents respond by bringing food closer to the ground which helps protect the fledglings from predators.
The male mockingbird continues standing guard over the fledglings and chasing away potential threats as the female provides most of the food. Both parents lead fledglings to good foraging spots. The young begging calls gradually fade as they become more independent at 2-4 weeks post-fledging.
Even after stopping direct feeding, the parents remain with offspring as they refine their flight technique, build stamina, and learn to self-forage. This family group association persists for 1-2 months until the juveniles disperse to establish their own territories. Most mockingbirds first breed at a year old.
Conclusion
This overview of the Northern Mockingbird’s breeding ecology shows the fascinating behaviors and adaptations involved in attracting mates and successfully raising young. Elaborate courtship displays lay the foundation for pair bonding between males and females committed to cooperative breeding. The male and female share duties of territory defense, nest building, incubating, and providing extensive parental care to ensure robust offspring survival. These rich social interactions help maintain the mockingbird’s abundance as a staple North American songbird. Ongoing research continues revealing new insights into the mockingbird’s complex reproductive biology and behaviors.