Meaning: 'Blend' means to mix or combine smoothly with something else, in this case, the nightjar's appearance with its surroundings.

Wrong options:

• sneak: The word 'sneak' implies moving stealthily, which does not directly relate to the visual aspect of camouflage and does not fit grammatically as a synonym for blending in.
• hide: While 'hide' suggests concealment, it does not convey the idea of merging visually with the environment as effectively as 'blend' does.
• scream: The word 'scream' is unrelated to the context of camouflage and does not fit grammatically or contextually, as it implies a loud noise rather than a visual characteristic.

Correct answer: makes

Explanation: The verb 'makes' is appropriate here as it indicates the action of creating or establishing something, which in this case refers to the bird's judgement leading to its camouflage success. It fits grammatically and contextually, as it describes the result of the bird's decision-making process.

Meaning: 'Makes' means to cause something to exist or happen, indicating that the bird's choice results in effective camouflage.

Wrong options:

• rates: The word 'rates' implies evaluating or assessing, which does not fit the context of creating camouflage and is grammatically incorrect in this sentence structure.
• wants: 'Wants' suggests a desire, which does not convey the action of producing or establishing something, making it contextually inappropriate here.
• awards: The term 'awards' refers to giving recognition or prizes, which is irrelevant in this context and does not fit grammatically.

Correct answer: based

Explanation: The word 'based' is correctly used here as it indicates the foundation or criteria upon which the birds choose their nesting locations. It fits grammatically and contextually, as it relates to the specific patterns and colours that influence their decisions.

Meaning: 'Based' means to use something as a foundation or starting point for a decision or action, in this case, the birds' choice of nesting sites.

Wrong options:

• according: The word 'according' is typically used to indicate agreement or reference, which does not fit grammatically or contextually in this sentence structure.
• for: 'For' does not convey the idea of foundation or criteria and is grammatically incorrect in this context, as it lacks the necessary structure to indicate basis.
• raised: The term 'raised' implies lifting or elevating, which is unrelated to the context of choosing nesting sites based on patterns and colours.

Correct answer: both

Explanation: The word 'both' is suitable here as it indicates that the birds enhance their markings in two specific ways: within a habitat and at a fine scale. It fits grammatically and contextually, as it emphasizes the dual aspects of their camouflage strategy.

Meaning: 'Both' refers to two items or aspects being considered together, highlighting that the birds' choices affect their camouflage in multiple dimensions.

Wrong options:

• seldom: The word 'seldom' means rarely, which does not fit the context of enhancing markings and is grammatically incorrect as it does not relate to the duality expressed in the sentence.
• seldomly: Similar to 'seldom', 'seldomly' is not a standard adverb and does not fit the context or grammatical structure of the sentence.
• crisis: The term 'crisis' refers to a critical situation, which is irrelevant in this context and does not fit grammatically or logically.